Cannot log in to HA after core-update (HA on Syno VMM)

Ok, so I am new to HA and spent a good amount of time and effort setting it up, configuring dashboards and all. And then yesterday, after installing the HA-core-update - I can’t seem to login.
I have extensively searched and read all the variations on this topic (clear browser-cache, cookies, different browser) but that does not do the trick unfortunately. I am using Dashlane for passwordmanager and am 100% sure I have saved the username (and not name) and correct password.

I am running HA on my Synology NAS in a Virtual Machine (called VMM). I have read some things about changing files, deleting files and/or folders - but I cannot for the life of me find out how to connect to the folders and files on VMM! (and yes I did google that) Running MACOS and no Windows in my house (not literally…) to check or try something else.
So if there’s anyone running a similar setup with HA on VMM - please advice me how to manage my HA-files…

And ofcourse I can make a new virtual machine and start over again, and if necessary I will - but how do I prevent being locked again?

Can you connect to HA from DSM → virtual machine manager → select your HA → Connect ?
What does it says there? Any errors? Did you try to restart HA from there (click on arrow right of “Shut Down” and select “restart”)?
If you can ping you HA’s IP then try to connect to it with putty - if succesfull you’ll have access to all files to modify them.

Thanks for replying Pavel, much appreciated.
Can you connect to HA from DSM → virtual machine manager → select your HA → Connect? > Yes I can and have done. Explored a few commands there, tried auth for new password but failed with the errors msg “Error: unknown error, see supervisor”
Did you try to restart HA from there (click on arrow right of “Shut Down” and select “restart”)? > Yes I have done that a few times to no effect.
What does it says there? Any errors? > No errors, just the command line prompting at me.
If you can ping you HA’s IP then try to connect to it with putty - if succesfull you’ll have access to all files to modify them. > I am not quite sure what you mean by ping - I know it’s a Windows commandline but am not familiar with the Mac-equivalent…

ping is standard network command to see if device is responding over the network or not (something like I’m alive). - no idea about Mac, but this is first result on google -How To Ping On A Mac | Macworld
Because of the error in supervisor log, I would suggest you try command ha supervisor log (I think that’s the correct one, but you can just type ha supervisor to get list of all commands) or ha supervisor status. Do that in this window.
As for the password - it doesn’t change by itself - so probably wrong one is saved

Thanks for replying. I was searching for scroll-options in Hasio because the logs are too long for one page. Didn’t find it - but I did the command login which presumably opens the shell. Prompt changes from ha > to #. But… I am not sure what has ‘opened’ and which commands I can use here, any clue?

Ok managed to flick through the su logs: “WARNING (MainThread) [supervisor.auth] The user 'MJ' is not registered”.
That would suggest that my username is not correct. But again: I am 100% sure that I entered this in the username-field when onboarding. Double-sure because I clearly remember my name-value was “Matthijs”. And yes I have tried to login with that username but no…