Switching refrigerants can be problematic if not done properly. The oil used in older R22 systems is not compatible with 407C and can gum up the system and plug the metering device and evaporator.. That causes the system to pump down all the refrigerant in the low side to the high side and stop doing any further useful work.
It's so labor intensive and time consuming to get all the old petroleum based oil out of the system that it's usually not worth doing a conversion unless the compressor is being replaced. The replacement compressors have compatible oil in them.
Then it's also possible that you got some contaminant into the system that is causing the problem.
A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! Helping You to Do It Yourself!