Solved! Go to Solution.
This happend once to me because the "build specification name" at Build exe windpw was too long, try to change the name of your exe file.
Just confirming LV 2020 in Win10 - that this still is an issue...By default LabVIEW 2020 create a default RT path is this too long..[see image] I changed the temp Win RT build directory to a simple Documents\LV Builds
...and it works...