I have had that happen and there were different causes.
1) Open a separate window and check you job history. Sometimes it submits, but it doesn't show
2) There is a question unanswered, that does not generate an error message. This tends to be the most common problem that I have. There is a question I overlooked somehow, but there is not an actual error message to tell me which one to check.
3) the site isn't working at the moment, so try again in a bit.
Are you using IE to complete your shops? I personally find that it does not work any better for me than other internet platforms, but if you contact support and were not using IE, they will state that it is your cause.
Make sure you have all your narrative saved in a separate document, so you can just cut and paste it back in.