I spent months trying to fit my novel into a genre suggested by the man. assessment. I could not make it work. Eventually, I went back to my first version (pre-assessment), re-read it and realised it was still what I wanted to write.
I did try sending my MS to a few agents a while ago. Only one reply - a standard 'no thanks, not for me'. I'm getting on a bit and can't waste months, or even an entire year, waiting for responses which may or may not come. I'm looking at self-publishing now.
Didn't the agents you submitted to suggest the time you could expect to wait for replies? If that time has elapsed, find some new agents to contact, if you wish to continue the traditional route. As others have said, if the one who requested the full hasn't had the good manners to reply, s/he is not worth bothering with.
We tend to forget that agents are businesses. If they don't give good customer service, take your business elsewhere.
Whatever you do, don't be disheartened. Many of us have felt like that.