I don't know if it is normal, but I'm beginning to think so. I have submitted 3 over the past week and have not received a response to any of them.....
Yes it is quite normal for them not to respond at all - or for their reply to be labelled as 'Spam' (because of it's URL) by your ISP and sent to a junk/bulk folder - it is also quite normal that if you are lucky enough to receive a reply it will be one of their pre-typed "Standard" replies which will have no bearing at at on your original question.
That is why these forums are so popular - ask your questions here - your much more likely to get a useful response.