@Zet Man at first i did follow through correctly but i had ran into another issue doing it that way (maybe related to how i host) when i kept the original configuration folder and removed the rest of the old OSSN files (except data) i got this error in pic. so i had to redo the whole configuration again to get it working again

Edit: not sure if it could be xampp related cause i do host at home and i know thats not recommended. but the site does work. right now it is just the youtube links now not displaying. everything else is running perfectly

Edit: its basically a fresh install now except the database and ossn_data but yeah still no youtube videos showing up in posts. just blank while other posts and comments still working 100%

Stefan,
your report makes me wonder: If you followed the instructions correctly - especially

Remove old Ossn installation from your site, `except the folder named configurations` and your Ossn data directory.

the configurations folder should have been left in place. Actually, none of the files in it are touched by the upgrade process, and that's why I don't understand why the trailing slash should be missing all of a sudden?!?

@Arsalan Shah actually now youtube video links are not showing. just a blank post. no error logs have came through when i turned it on and refreshed the news feed.

@Arsalan Shah found it out thanks. if anyone else faces this issue check your ossn.config.site.php again mine had a missing "/"

it was $Ossn->userdata = 'D:\ossn_data';

instead of "$Ossn->userdata = 'D:\ossn_data/';" <--- this layout was the correct one

requires the "/" at the end of the destination link

Enable error reporting in your admin panel -> basic settings. And reload newsfeed page again now go to your file manager and find the error_log in root of OSSN files. And let us know what you see in it.