FileRun stuck at "Siginin in ..."

I'm trying to get an old copy of FileRun to work after upgrading my Ubuntu to Focal.

Version 2019.12.25, PHP 7.3

If I try to login with any of the three user accounts, it gets stuck at the small window saying, "Signing in..."

And there is nothing written in any of the logs nor on the web page.

I have removed .../system/data/filerun.dat

All the Paths are the same, as per the document that shows which database tables the file paths are used.

The only difference is that I'm now trying using Localhost instead of the Domain that I used previously.

Is this likely to be an issue? If so where in the database or files is the domain stored.

Any other reason?

Thanks