Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Of course feedback is good, sorry, no offense intended. And: oh yes, I did so wait for this - didn't expect this day to come any more. Especially as this is actually not reflected in any of the publically available roadmaps for O365.
But still I'm not sure I understand what your problem with the first address (for your own account) is:
You say you can generate it (which is also what your screenshot shows).
So your first try didn't work, but a day later it did?
I did generate mine perhaps 30 min after connecting the domain and it worked immediately.
I just deleted it and created a new one - also works.
From my point of view I can also not yet see the feature to add other users as @szymonBis reports, and certainly I can not see a way to add extra addresses on top of that... But let's wait and see.
BR southy