I'm not sure why that is?

One guess is that perhaps Gitea didn't like the password you set?

Or are you perhaps using a keyboard that isn't US-International compatible? In that case, some characters may have been misinterpreted when you set the password initially, but then interpreted correctly in your web browser?

You can try again by re-running the first boot script, like this:

/usr/lib/inithooks/bin/gitea.py

PS apologies that my response was so slow...