If the user is logged in locally on the target (remote) Windows 11 machine via PIN = RDP remote login with the same identity (MSA) does NOT work.
If the user is logged in locally on the target (remote) Windows 11 machine via PASSWORD = RDP remote login with the same identity (MSA) DOES work.
My Win11 target PC only gives me the option of Pin Login so I had to follow the "reset Pin" workflow, login with the MSA via username/password, and once logged in cancel the rest of the Pin reset, and then it proceeded to log me into the target machine OK, and then I was able to RDP from the second PC to the target PC using the MSA identity.
if I then close the RDP session to the target machine, then go back to the target machine, sign-in via PIN this time, then try RDP using SAVED credentials in the RDP session - I get the "login attempt failed" / "Your credentials do not work" message. If I then RE-ENTER the password manually and re-try... it DOES work.
So something is borked around the cached credentials / Pin / Saved RDP credentials / whatever combo that means sometimes it just work authenticate.