In case of Gimp-2.10.36 and G'MIC 3.5.2 you should get a message about missing libnghttp3-9.dll file.

Copying dll to gmic_gimp_qt folder solves the problem.
This problem was also reported here:
https://discuss.pixls.us/t/release-of-gmic-3-5/44490/1Required file from Gimp-2.10.38-1 (gimp.org) in attachment.
However you should update your Gimp to version 2.10.38-1.
It's easy: download, install on C and move (replace) directories in portable version location:
32\
bin\
etc\
lib\
share\
If you change directory name from Gimp-2.10.36... to Gimp-2.10.38 you need to edit file location in Preferences.