I have upgraded from groupoffice-6.4.150-php-71 to groupoffice-6.4.191-php-71, and then to groupoffice-6.5.84.
I remember I skipped previous upgrades because of this error, but now I decided to fix it finally.
After the first upgrade step, my login page does not appear (this is true to any versions above 6.4.150), only an empty white page. But it is not completely empty, as HTML source can be displayed, and it looks good. Also, install/test.php is displayed properly, and shows no critical issues.
I don't see any errors in the httpd logfiles.
And to make it more strange, activesync works (it has been set up before).
I have a reverse apache proxy in front of this installation. But if it would be the source of the problem, activesync would not work, and neither the install/test.php.
Can you help me figure out what can cause this? Where shall I look for hints in my system?