Interesting one that has so far stumped the Groupee Support too so throwing this one out to the wider wind...

After upgrading UBB Classic from 6.50 to 6.73 (I backed everything up first and took screengrabs of the settings), the existing list of 4 Forums are no longer visible.

I've checked the existing paths structure (same as before), checked 755/777 permissions, rebuilt all 4 options in the Control Panel and the Forums still aren't showing up through the standard... /cgi-bin/ultimatebb.cgi? route.

Only if I did a direct URL such as the following:
/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=000115;p=0 or
/cgi-bin/ultimatebb.cgi?ubb=forum;f=1;hardset=0;start_point=0;DaysPrune=0

...(changing f for Forum Number; t for Topic Number) will the Forums and Topics show up.

Any ideas guys?

Your help would be truly appreciated.

Thats a tough call since there are only a few people that visit here that still use classic.
But anyway I recall there was a file in the forums folder that held all of the forum data, not the posts which are in a separate folder but one for all of them.
Probably one of the var files which you should not over write if existing during a upgrade.
You said you had 4 forums so you should have four folders ,forum1 ,fourm2,forum3 and forum4.
But there is another file that I believe was just above them in the path to them.
I would guess you have a corrupted file.

But it may be better to just restore your old version in another folder check that it works then upgrade again. if that works then move classic to the old location and update your var files per the documentation for moving.

Well, if you're upgrading to threads it should import all of your old stuff (you'll likely need to re-assign categories though).

Classic had a cache, have you tried purging all files in it?

Well he already stated that groupee was not able to help.
He is upgrading within the 6.x series.
So I would suspect a corrupted file due to:
1. Wrong file type transfer used.
2. Overwritten file that should not have been.
3. File corrupted due to dropped connection during transfer.

vars_forums.cgi


Contents Example:

1|^|Forum 1|^|Forum 1 Description|^|On|^|is not|^|is|^|allreg&allreg|^|SGKPMU|^|1|^|default|^|ON|^|yes|^||^|all&all|^|000001|^|date|^||^|1


This should give you an idea how to rebuild the file. One line per forum in this file.

Thanks guys. (All) your help here is really appreciated.

Here's the first forum's code. The other three have the same structure. Can you see anything awry in it?

|^|AIRWOLF THEMES Discussion|^|Air your constructive views on AIRWOLF THEMES products - past and future|^|On|^|is|^|is|^|allreg&allreg|^||^|1|^|1000|^|ON|^|no|^||^|administrators,moderators&all|^|000001|^|date|^|This Forum has been set up to allow Airwolf fans and the Wolf Pack to air their views on Airwolf Themes products - past and future.|^|0

Not really sure. I can't remember what each value in the array is for but if you are going to try to repair the board and not re-install. Here is what I would do.
Add a forum in the control panel. Make the settings for what you would have for the existing ones.
Make a test post. If it works double check the new forum in the var file against the others.
Then just disable the test forum from view.
Should take a whole 5 minutes to do and this should at least verify something is working at all.

NOTE:Old school teaching from classic was always never delete a forum just disable it. And recycle for a future forum.

Just tried adding a 5th Forum. Doesn't show up either when the boards either in Admin mode / fully Open Mode.

/cgi-bin/ultimatebb.cgi

Rebuilt the Meta-Data and Cleared Cache again. Still no difference. This is SO frustrating.

Okay I feel your pain.
I would double check your permission settings and also look at the file sizes for 0 bytes. The could be a clue to a bad/corrupted file.
I am talking all of the files.
Like I posted before it might be more simple to restore the backup. Get it working and deal with the upgrade on a different folder to test. Since I see your site has been down for this duration.
BTW I have never seen a issue like this upgrading within the 6x version. But from 5x to 6x all kinds of things happen especially when the code was modified.

There's a vars_cats.cgi file sitting at 1-byte in size, which is empty when I open it in a text editor?