[BirdOPrey5]

OK there is no built in setting to get subforum posts to show up in the main forum. I have a mod that does this, it requires modification of the forumdisplay.php file.

The mod is here: https://vborg.vbsupport.ru/showthread.php?t=245414
It also links to a thread where getting sub-forums to show in the main forum was specifically addressed.

But if what you are saying is you want sunforum posts to how up in SEARCH results, that would be the default behavior. The old admin may have specifically excluded some forums from search results... Open the navbar template in the template editor and search for "search.php" - I think there are 9 standard occurrences of "search.php" in that template... look if any of the links have the code "&exclude=X,Y,Z" on them where X, Y, Z are forum id's of excluded forums in the search results... if so just remove the 'exclude' statements and it should work as normal.