Also, reading the ERROR you've shared in your initial post,

Warning: include(): Failed opening '/libs/' for inclusion (include_path='.:/usr/share/php') in /users/ on line 9

it looks like you have an invalid path there:

change to:

...or whatever the correct absolute path on your server should be.

And this is the reason why your initial install would fail.

isaac @ // my forum @
a current developer of UBB.threads php forum software // 7.6.2 Released