I recently performed an upgrade of a bunch of extensions on our Joomla site (the site is running Joomla 3.8.6 and was upgraded from 3.8.5 at the same time).
I tested the updates on a stand-alone test box and confirmed everything was working, then repeated the same updates on the production system.
On the test box, there are no issues. However on the production box, we have two (possibly related) problems.
Account activation emails are sent, but clicking the link fails to activate the account; it simply dumps the user back to the site home page, without any confirmation or error message.
Password reminder emails are not sent. After entering a valid email address, it simply dumps the user back to the site home page, without any confirmation or error message.
I'm specifically asking for help here with the first problem as that's the one I'm tackling first, but I mention the second as well, in case they are related.
As stated, the test system is running apparently identical software, but does not present either of these issues.
There are no obvious error messages in any logs, nor does anything show up if I turn on debugging and error reporting.
There is one thing that seems weird, which may be relevant: in both cases, after redirecting to the site home page, we get an additional cookie
joomla_user_state = deleted. I can't work out why this cookie would be appearing, but I am assuming that it's relevant to the issue somehow. I have searched the Joomla code base (and all the extensions), and I can't find anywhere that sets this cookie to
deleted (or indeed to any value other than blank).
My current best guess is that one of the user plugins is doing something bizarre before the user record can be saved. But I can't see anything wrong there, and as far as I know, none of the extensions that were upgraded were user plugins.
Can anyone please help me understand what's going on here?
I'm happy to add further detail if there are any questions that might help.