Does it make any noise at idle, while indicating zero pressure? Did you buy a quality gauge & sender, and install it with new fittings, or verify no blockage in your fittings?

Since you have to pull the engine to pull the pan, you might consider draining your oil, letting it drain totally, then re-fill with five quarts of new 10W30 and check your dipstick, before you start the engine to verify your "Full" mark. If you also change the filter, then refill to your verified "Full" mark on the dipstick and see what your pressure does? That's an easy step to ensure proper oil level.