Copying comparison file removes Interpro2GO

I have a comparison file which includes Interpro2GO classification. However, when I copied it and opened the copy (to preserve my painstakingly manually colored samples in one file while doing it in a different way in the second file), the copy does not allow me to show the Interpro2GO classification. (on the same computer, in the same MEGAN version, which still shows the Interpro2GO tree in the Properties).
It is greyed out both in the Icons and in the Navigation menu.

Edit: I just tested to copy the original file again and this time it did not happen. Maybe it happened during loading in some extra metadata (which failed loading and all metadata had to be re-imported)?

I’m not sure what you mean by “copied it”.
If that means using the OS to make a copy of the file, then I am baffled.

Here is something that you can try:

Select Edit->Properties->Enable Software Feature…

and enter

open-empty-fviewer

Then restart or open a new window. Now all functional viewers can be opened, whether they have data or not. If you data is still there, then you will see it.