"Preferences" hangs on upgrade

Describe the problem you’re having:
I am upgrading from V1.13 to V18.12, using Installatron/Control Panel. I have renamed the old installation, exported the OPML file from V1.13 and completed the installation of V18.12, with no error messages.

I can open and log on to the new installation, and the TTRSS system messages appear in my RSS feed. But when I open Actions>Preferences to import the OPML, a “loading please wait message appears” and the system hangs.

I have changed the permissions for the php files to 0755, but that doesn’t fix the problem

tt-rss version (including git commit id):
V1.13 & V18.12.

Platform (i.e. Linux distro, PHP, PostgreSQL, etc) versions:
Windows 8.1, 64bit with both Firefox and Chrome. My hosting company runs MySQL Version 5.6.41

Please provide any additional information below:
V1.13 works fine

Thanks for any assistance you can provide!

moving to unsupported

Maybe you should ask them?