Artc

Well, mine is finally working. I gave up myself after trying multiple different tricks ... reinstalls etc.

But, I was able to locate a private dealer. This guy worked as a mechanic at the VW group for 25 years and has now gone off on his own and set up a VW group-approved  garage. He actually knows what he is talking about (for example the protocol for comms on the Q3 is the old slower one as opposed to the other models). Anyway, he updated my software and was able to fix the key user etc login issue; and recover all my radio, navigation favorites from my account at Audi. So, I am now a happy man!

My problem was all about the latest MMI system update. It was described in detail to me by a certified VW/Audi workshop (run by a guy who worked for the VW Group for 20 years). He explained how earlier updates caused said instability. And he will be doing a complete baseline installation & update on my Q3 in 10 days time. If need be he will even create a new profile for me (credentials are not the issue, but this is my 4th Audi in 17 years with same profile which has not worn well).
Will keep you posted

HI,
Worthwhile trying, but didn't work for me.
I redeployed the app and changed the pwd & got as the reset - did a "soft-reset" .. meaning holding the volume control knob for  ± 15 secs . When it comes up I see it verifying my original/current key user (lets say XXX) for access ... and then  I get the user dialog. XXX is still listed alongside 'Guest' but I cannot apply its settings (tech error) .. I cannot delete XXX .. and I cannot add a new user with the new password: "technical errors" everywhere.
The only option I see is do a full factory reset (the nuclear option) .. but I understand I may need dealer approval with registering a new user 😞
So still stuck ...
This whole key user thing has always been unstable; I had issues with my last Audi too and had to leave it at the dealer.
In any case, if anyone has any suggestions/advice it would be welcome