Your issue is due to the below fatal error.


This is due to a 3rd party CB plugin called "CMC - Newsletter registration" found within CB > Plugin Management. As it's throwing a fatal error and it's also loaded at the top (plugin order determines load order) it means CBSubs never gets a chance to process registration.

Once "CMC - Newsletter registration" is disabled everything works fine.

If no plan is selected then CBSubs isn't going to do anything (ensure your plans are set to default and exclusive so they're always selected). You also need to be concerned with caching issues. If page cache is kicking in then it's going to mess up the process (no forms should ever be cached). Cancelling the basket for 1 user should have no effect on the attempts of another to register. Enable debug mode and maximum error reporting in Joomla global configuration then retest your usages (this is how I found the bad plugin) to ensure no other errors are occurring.

Something installed is messing with the $user object. It's passed by reference throughout CB. If something unsets it then it's going to break CB. Disable non-core CB/Joomla plugins/extensions 1 by 1 until it goes away.

I can not stress the below process enough to avoid these problems.

1. Enable debug mode
2. Set error reporting to maximum
3. Install extension
4. Test
5. Enable extension
6. Test
7. Configure extension
8. Test

This should always be the process. You always need to be aware of the before, during, and after. Having debug mode and error reporting configured ensures errors, notices, warnings, etc.. are always exposed. The only notices you should ignore are strict standards. Nothing else should ever be ignored and should be fixed as soon as possible.

Skipping the above process and installing, configuring, installing, configuring, rinse repeat will guarantee cause issues and you'll have no idea what installed is doing it without constant debugging.