both email and username can also be accepted.
have you configured the config.php and config.ini? by looking at the page still showing the default company name, i think it's still yet to configure.
can you verify the if the db exists in the location? and the permission?
you may also run a quick check if everything is set correctly.
run these in terminal
sqlite3
.open /xxx/xxx.db
select * from mailbox where is_admin=1 and local_part='xxx';
if it returns result then it's should be good to go
