Agnantero, As you read through threads you will discover that there are a limited number of slots on the server for each map type. So as games finish others can start. Unfortunately there are some players who have multiple maps open, which limit the broader community. This is a topi of discussion. My first suggestion is to join a game on that map that is already created and ideally has not started yet. Otherwise you will need to wait and keep trying.
"A good plan, violently executed now, is better than a perfect plan next week." - General George S. Patton, Jr.