Curl returning empty
When I run this command from curl i am getting empty response
curl curl:password@localhost:8081/oauth/token\?grant_type=client_credentials

Am I missing anything?
Can you try to use a POST HTTP request?
curl -XPOST curl:password@localhost:8081/oauth/token\?grant_type=client_credentials
Same again

Ok, then please add the -v flag to curl for verbose output, it might give us a hint for what is going wrong.
curl -v -XPOST curl:password@localhost:8081/oauth/token\?grant_type=client_credentials
It is showing 400 Bad Request

Ok, I checked it and it worked for me. I think the problem is that we escaped the ? in the curl command because it's necessary in a bash, but since you're on Windows it's actually not needed. Meaning, please try
curl curl:password@localhost:8081/oauth/token?grant_type=client_credentials\