"This is not a Valid String" when changing theme

I am working on a clean and newly installed system. When I try to change the theme, I get a message that this the theme is not a valid string. Screenshot%20from%202020-04-08%2015-07-22

I get the same message even on the default theme. Any ideas? (Note: For testing purpose, I have set cache directory, and its content permissions to 777).

Hello @Omar_Khan! Did you manage to find out what was wrong? We are getting the same error, but on OMP, after upgrading from 3.1.4 to

Hi @mannemark,

You might want to create a new post and describe the issue you are experiencing there, as this is quite an older post and it’s likely the user is not monitoring it any longer.

Best regards,

PKP Team