That’s good!
Hm, I would recommend reading this section here in that guide - I could imagine you may have a master password with some problematic characters and/or some kind of auto-corrections changing your input.
So you could either try to input your master password differently / copy & paste / don’t copy & paste / deactivate auto-correct / … - or maybe even change your master password to a passphrase. (but I wouldn’t do that last idea immediately - and if at all, create an export before you do anything!)
If it isn’t that, I’m probably out of (immediate) ideas…