I Personally suggest you to Manually Install WordPress by creating Database and user that too manually and i hope that will work for you.
Hey There,
As far as i am concerned if you are sure you are typing a valid username then you should try re-installing the wordpress.
Anyway its gonna take just 5 minutes.
Thanks
Howdy,
You need to see first that their must be all required permission.
If everything is perfect then look weather the details are type correctly and Case-Sensitive.
