Sorry, but without seeing your files I can't say what could be wrong on your end.
It's up to you how you upgrade your board, if you're doing it on your own. Just a month ago I've updated couple of forums which was running on the 6-years old versions of miniBB. No problems so far.
It all is working, if you follow all instructions from the Updating History carefully and do not use "blind" method during this process, while you're just doing something but not sure what are you doing :) I can't help you in that.
Refer to our premium support
if you are in troubles and your older miniBB is *too old* to handle it by a non-coder.