Welcome to the forum too.
What is your pressure? That tells a lot. High pressure indicates a pressure side blockage while low indicates either a suction side lockage, gunked up impeller, or air being sucked in. The gurgling in the heater could just be trapped air that isn't being purged due to insufficient flow. Can you see air in the pump basket? If it is air leaking in on the suction side look for the obvious first like the gasket on that pump basket lid. All it takes is a very tiny air leak to mess things up. We'll figure this out.
Al
Edit: I just read the post again and you said no pressure. Are you saying the gauge is reading very low or just no flow to the returns?