Do you hit the 'create" button and it just returns you to the top of the page with no explanation?
Then check:
The name is all lower case
There are no trailing spaces from autocomplete at the end
Especially on mobile, the errors are currently poorly flagged up (I hear it's better on the desktop) and those have been the two most common errors that I've seen.
Are you doing it from mobile or from an app? I tried the other day and it would error but not show what the error was and just scroll up to the top of the form.
I ended up loading the desktop view from a laptop and was able to create the community