Seems like every couple of years, I can't get my pump to prime to save my life...Makes relatively little sense, but running some water in through the water connection seems to do the trick for me. Yeah, open faucets, but they are generally uphill from the pump and it's just a little bit hard to get things over the magical hump.
But, it's classic Murphy's law, about the time I give up...something is WRONG...well, let's try ONE MORE TIME... re-re-re-openin a faucet, re-run some city water, re-open a low point drain, re-put a little more water in the tank... bzzzzzzzzggggggrrrrrrrummmmmmmmmmmmmm- WATER!
Good luck.