I have been on roll20 for 2 years and I can tell you you need to be patient. Often people make the mistake of applying to games that are full but the GM forgot to take down the LFG fown or applying to games that are filled to the brim with applicants. It's better to take sometime and try to apply to new games as they come up.
Also another key is to make sure you read and follow any application instructions the GM lists. Failure to do that gets you ignored. Also when you do apply be polite, use full sentences, and proof read before you post. Make yourself stand out. Post like "can I join your game" generally get ignored. Also try using looking for group forums as well since some people advertise there instead.
