The same issue happened to me today, but none of the answers was helpful. the problem is currently only project owner can create it.
I am the editor, that is why I am unable to create it.
Check your role in Project overview -> Users and permissions. if you are an editor ask the owner to create it.
Note: This error did not happen to me when I create a new project. It happened to me when I create Firebase Storage in my firebase project. but I got the same error message(There was an unknown error while processing the request try again).
If someone searches help by error message this answer may help to them. (I also got this question by searching the error message)
hope, it is helpful to someone!