Logged out and back in on the old forum.(this forum)
Followed the prompts to migrate account.
However, when I log into the new forum my MM user name shows.
Yesterday I was logged in to the new forum under my old name.
>However, when I log into the new forum my MM user name shows.
That is the way that it is going to work from now on.
You could follow JC's advice and first change your Adobe Forum's Screen name to something else (it's going to become extinct anyway);
and then log-in to your MM/Adobe ID Account and change your Screen name there back to your former Adobe Forum's Screen name.