Large Windows update; lost access to my userid...

I've been away from my Windows 10 PC for a couple of months. Shortly after turning it back on it started nagging me about a fix that was so big, I should schedule a time for the update. I postponed it.
When I came to my PC this morning, I signed in with my userid (Steve) and password as normal, and the fix started to apply.
So I waited. Eventually the system re-booted and I could no longer logon as Steve. Then I noted that it was telling me that I should be using my Microsoft Account password. Until today, "Steve" has been a local account. I tried my Microsoft Account password (got it from LastPass on my phone) but was told the password was invalid.
I went to account.live.com/password/reset and reset my password. Tried to logon as Steve, but now my new password was invalid.
Changed my Microsoft Account password again, and still I cannot logon as Steve.
There's a bunch of other weird stuff going on, but let's not confuse matters.
Any suggestions how I can get to my "Steve" ID? Incidentally, I renamed it to Steve_Old and created another (Local) "Steve" ID, and that's what I'm using now. But Steve_Old has some EFS encrypted files that I'd like to recover.

Yes, my computer is connected to the internet when I try to logon.
But it turns out that my ISP has had a couple of catastrophic outages over the past two or three days, causing connections to drop and then recover.
So, it is probably worth having another attempt, especially as I just logged into the Microsoft Community with my Microsoft Account password, so I'm sure that I have the right/current password!
I don't think I could take the disappointment of it not working now, so I'll probably go to bed and try it in the morning.

Morning has arrived (in our part of the globe) so, with some trepidation, I tried to logon to my "Steve" userid (renamed to "Steve_Old").

It worked! And I have access to all of my EFS encrypted files!!!

I plan not to rock the boat for a few days, but then I will:

1. Rename the new local account "Steve" that I created to "Steve_New"
2. Rename account "Steve_Old" back to "Steve"
3. Reset account "Steve" to a local account

I'm just a bit leery that doing this might remove access to my EFS encrypted files again. I know it shouldn't, as renaming userids and swapping between local and Microsoft Account are both supported/documented processes, in theory safe. But this is a case of "once bitten, twice shy" ☺

Does anyone have recent experience of doing this sort of thing? I plan to backup all my EFS files before proceeding anyway.