Same issue here.
It appears to be trying to read PluginLoading.txt in “%appdata%\Grasshopper” but if I look in the folder the file is missing.
Sometimes when I get this message it results that several plugins are absent from the ribbon.
the error dialogue seems to come up randomly in my case.
That PluginLoading.txt file seems to be written and deleted on startup.
I think it tracks plugins as they load and only keeps the txt file if a plugin crashes.
I tried to copy the file during loading time to check contents. I repeated several times ad every time It was tracing a different plugin.
C:\Program Files\Rhino 6\Plug-ins\Grasshopper\Components\GhPython.gha
if I copy the captured file back into the folder I get this dialogue:
which is not true.