Forum is running and login works!
But now the forum shows me in Admin Area that there are modified files:
Some of the source files for Invision Community have been modified.
/www/htdocs/w00afc19/start/forum/applications/core/extensions/core/MemberFilter/Achievements.php
/www/htdocs/w00afc19/start/forum/applications/core/extensions/core/MemberFilter/ProfileFields.php
/www/htdocs/w00afc19/start/forum/system/Content/Content.php
/www/htdocs/w00afc19/start/forum/system/Content/Item.php
/www/htdocs/w00afc19/start/forum/system/Login/Handler/OAuth2/Custom.php
/www/htdocs/w00afc19/start/forum/system/Login/Handler/OAuth2/Google.php
/www/htdocs/w00afc19/start/forum/system/Member/Member.php
/www/htdocs/w00afc19/start/forum/system/Text/Parser.php
You should download an unmodified copy of those files and upload them to your server. Once that is done, check if the problem persists.
Can I download the unmodified files without lost of information?