from the title of your post, i'm assuming you do have a txv. you didn't mention it in your actual post. if it is, charge until you have 7 to 10 degrees sub-cooling, then check your superheat. if the coil is starved due to low feed, the superheat will be high. with a txv, if you have properly sub-cooled liquid fed to the valve, the remote sensing bulb will take over and maintain superheat. we need to see the pressures and line temps to diagnose. a failed power cap would result in a total pump down. it may actually pump into a vacuum. if there is some pressure, the problem is a valve not feeding, a restricted inlet screen or possibly a partially restricted liquid line filter (not common, but happens).