No mistake that I can see. And even if there is one, KiCad shouldn’t be telling you the resistor is unconnected here. If there is an issue with the net, it should be specific about that issue.
The only real reports are on R13 and the ones on the global labels Rx, Tx and Reset. Everything else can be ignored for now.
Sorry misread your answer, great solution!!
but about the other errors:
I tried to disable ALL option of the ERC but no difference!
agreed, the power flags are my bad, have to figure out how that need to be sorted yet.
But setting all ERC options ‘off’ and still getting error does confuse me so that’s why I spent the last 2 day searching for a solution
The checks done for not connected and power pins driven is always done and not part of that matrix.
I found out that there really is something strange with that schematic in general.
I assigned random footprints to it to continue testing. The resistor R13 really is not connected on the board if i import the connectivity information.
I also noticed that the crystal is not connected to anything for some reason.
This is another very strange thing. If i remove the resistor R13 then i can no longer use the highlight net tool on these wires.
Also, the entire arduino chip (A1) is listed in the NETLIST without any ports connected although there are no error om most ports.
As said, maybe I have to start from scratch, maybe the schematic is corrupted in a way I cannot understand.
I’ll have to log off, thanks again evrybody for your help. Let me know please if I still have to file a bug report? Will try tomorrow to start with a clean sheet…
What was the original source of that schematic anyways? I wonder if it was orignally created in a very old version of kicad as there are strange footprint assignments.
Or did you use the version 5 eagle import? (The small GND label next to the cap near the crystal leaves me to believe this is a possibility.) Or did you (or somebody else) use a pre version 5 nightly to import this project?
To OP: I fixed a few small & simple beginner mistakes. The remaining are very weird and may very well be a bug in KiCad. Making all boxes green in the ERC check matrix is a very bad idea because it completely disables ERC checks. The remaining 8 ERC errors are not related to this.
When you hover over R13 and then drag it with “g” the wires are clearly attached.
Then I deleted the resistor and added an inductor taken directly from the default library, and attached it to diferent wire segments of the same net, and it still gives ERC errors on the newly placed inductor:
That is what @eelik already reported above 
The problem seems to be connected to the crystal or capacitor symbol but i can not find anything wrong with them.
I deleted most of the schematic, and found it strange I did not get “not connected” ERC errors on the ARDUINO_UNO_R3_DIP while running ERC.
(Placed an unconnected NPN next to it for reference)
The problem seems to be with the ARDUINO_UNO. Wen I look at it in the symbol editor all pins are set to passive and they should generate ERC errors on unconnected pins.
I deleted all wires near the crystal/cap/R13 constellation and made new ones only between the caps and the crystal. I can not use the highlight net tool to hightlight these connections. But if i delete and replace it with a copy of the resistor i can highlight the wires again.
But as i can not find a reason as to what is going on i guess a massive bug in kicad is somehow triggered by this schematic. (I seem to remember a similar report a long time ago. We never really figured out what caused it.)
I replaced the ARDUINO with a 27128 on a fresh copy and the ERC errors for R13 went away:
The errors on the Rx and Tx labels also went away.
This also indicates some kind of problem with the ARDUINO symbol.
It looks like if the pins on the ARDUINO_UNO are somhow not recognized as valid pins by Eeschema.
I don’t know if it is related to the supposed bug, but I personally can’t open the schematics with 5.1.0 (32 bit windows). I always get the following warning / error
Error loading schematic file “E:\Mes documents\KiCad_v5\MouseOleum IR board SHIELD\MouseOleum IR board SHIELD.sch”.
invalid hexadecimal number in input/source
“E:\Mes documents\KiCad_v5\MouseOleum IR board SHIELD\MouseOleum IR board SHIELD.sch”
line 7277, offset 6
Line 7277 of the file is
U 1 0 8860D03359D6C4F2
which is part of the component
$Comp
L V_Custom:Crystal Y1
U 1 0 8860D03359D6C4F2
P 8500 2650
F 0 “Y1” V 8200 2600 59 0000 L BNN
F 1 “16Mhz” V 8100 2500 59 0000 L BNN
F 2 “CRYSTAL” H 8500 2650 50 0001 C CNN
F 3 “” H 8500 2650 50 0001 C CNN
1 8500 2650
0 -1 -1 0
$EndComp
I did the same now but the problems around the crystal persist. (Delete the wire between R13 and the crystal and try to highlight the wire between the respective cap and the crystal.)
That is a good info. But why does your 5.1 report it while mine does not?
Wait is this possibly a 32 bit vs 64 bit problem? (Could be a separate bug.)
That’s a good question I don’t have any clue.
Edit : Full version info
Application: kicad
Version: (5.1.0)-1, release build
Libraries:
wxWidgets 3.0.4
libcurl/7.61.1 OpenSSL/1.1.1 (WinSSL) zlib/1.2.11 brotli/1.0.6 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.5) nghttp2/1.34.0
Platform: Windows 7 (build 7601, Service Pack 1), 32 bit, Little endian, wxMSW
Build Info:
wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8)
Boost: 1.68.0
OpenCASCADE Community Edition: 6.9.1
Curl: 7.61.1
Compiler: GCC 7.3.0 with C++ ABI 1011
Build settings:
USE_WX_GRAPHICS_CONTEXT=OFF
USE_WX_OVERLAY=OFF
KICAD_SCRIPTING=ON
KICAD_SCRIPTING_MODULES=ON
KICAD_SCRIPTING_PYTHON3=OFF
KICAD_SCRIPTING_WXPYTHON=ON
KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
KICAD_SCRIPTING_ACTION_MENU=ON
BUILD_GITHUB_PLUGIN=ON
KICAD_USE_OCE=ON
KICAD_USE_OCC=OFF
KICAD_SPICE=ON
I am still using KiCad V5.0.2 (Linux 64 bit).
I deleted the connection between the crystal and R13 on the circuit with the 27128 and can not highlight the connection between C4 and the Crystal.
Edit: Full version info:
Application: kicad
Version: 5.0.2+dfsg1-1, release build
Libraries:
wxWidgets 3.0.4
libcurl/7.64.0 OpenSSL/1.1.1b zlib/1.2.11 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.5) libssh2/1.8.0 nghttp2/1.36.0 librtmp/2.3
Platform: Linux 4.19.0-2-amd64 x86_64, 64 bit, Little endian, wxGTK
Build Info:
wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 2.24
Boost: 1.67.0
OpenCASCADE Community Edition: 6.9.1
Curl: 7.62.0
Compiler: GCC 8.2.0 with C++ ABI 1013Build settings:
USE_WX_GRAPHICS_CONTEXT=OFF
USE_WX_OVERLAY=OFF
KICAD_SCRIPTING=ON
KICAD_SCRIPTING_MODULES=ON
KICAD_SCRIPTING_WXPYTHON=OFF
KICAD_SCRIPTING_ACTION_MENU=ON
BUILD_GITHUB_PLUGIN=ON
KICAD_USE_OCE=ON
KICAD_USE_OCC=OFF
KICAD_SPICE=ON
I think i am going to make a bug report about that. Lets see if the devs have any idea what could be wrong here.