I filed a bug report. Eventually I was asked to test the new version. I was slow in responding. Now the bug report is expired. It's still a problem. Do I just file a new bug report, or is there something else I should do?
I don't see a reason to report a new bug.
As described in that bug report, you should perform further tests, post the results and then you can change its status. I suggest you use
New if the bug persists or
Invalid if it has been fixed in new Ubuntu release.