It seems I spent more than the ads yielded in earned revenue. It it just me? Maybe bad keyword targeting on my part. It was fun to try for about 1 year but decided to use that money elsewhere. Course my biz was local to door to door business card mini brochures worked the best for me.
I agree it can be a lot of things, make sure every process of the audience is perfect, put your self in their shoes.
If you were not making any money, then you need to examine your account. Look for keywords that are too broad and probably money drainers. Remove those. That would be your first step.