Hi Karl,
https://forum.vbulletin.com/forum/vb...ot-functioning
This link to a vBelletin similar sounding topic may provide some useful info. The individual user scenario appears to often be the user's browser blocking a browser extension such as Javascript or other which facilitates entering a post.
If it's only one user being affected it indicates it's generally something on that user's machhine. One test if not already done may be to use your login credentials from a different computer and see if it makes a difference. I assume you may have done that already from other devices, yet perhaps try from a device you nomally don't login from.
A screenshot of what you get (or don't get) may be helpful. For example, are you not getting certain screens, or are you getting normal screens and posting as usual but nothing then shows up on the forum. Grroups can be set to require moderation before something shows up, but I assume for the entire group, unless more granular here and yours was reset somehow. We know it's true you're in a class by yourself Karl.
Seems it's likely an issue for you or Brent Mills, leaning toward you. I suppose forum bug or incompatible forum upgrade could be it, but again, if just you then may be likely your interface.
Best of luck. Brent