Years ago (many years ago) I had a forum and somewhere along the way I purchased Pro Chat Rooms 6 for it. I was happy with it and (much to my surprise) I still have it.
So my question is I am wondering if Pro Chat Rooms 6 will work with phpbb 3.3.4?
If it was "many years ago" then it quite possibly will not work with phpBB 3.3.4, if for no other reason than a lot has changed in phpBB over the years.
You could always try installing it on a test board or there may be an upgrade/update that will work.
It is also worth noting there are a couple of chat extensions that work with phpBB 3.3.4 which you could try.
David Remember: You only know what you know and - you don't know what you don't know!
I now no longer support any of my extensions but they will start to become available here