ACP is fine, I can do all the things I need to do without a problem, but only ACP works, the forum is blank only.
I upgraded by copying the 3.3.1 entire package to the domain, minus the config.php of course.
I deleted vendor and cache folders
I ran the install/app.php and updated the DB. Then removed the install folder.
No problems encountered until I tried to browse the forum, all I get is a blank page.
ACP had a problem with an extension, disabled the extension and this cleared the problem.
Updated all the extensions that needed it.
Still a blank page only. ACP still fine.
All styles disabled and prosilver reset to default, still blank.
removed vendor and cache again... I get a page, though I can't browse topics etc, still bounces to a blank page.
re-uploaded vendor and cache, purged local cache and remote cache in ACP. Still blank.
tried re-adding the styles, guess what... still blank.
renamed ext folder to ext.daz, still blank
purged all local and remote cache, still blank
re-uploaded everything, still blank
deleted everything except the upload folder (files)
re-uploaded again... still blank
tried alternative styles... still blank