Dumb question, but you did evacuate all the air out of the system before charging it, right?
Not a a dumb question, and no because I don't have a vacuum pump. If I was to do it right, I would replace the filter dryer which you can still buy new
https://www.rockauto.com/en/moreinfo.php?pk=814923&cc=1003554&pt=6972&jsn=333 and then pull a vacuum on the system for ~20 mins before refilling with a measured amount.
Right now I just wanted to see if I could get it working so I was not being picky about the details. If it continues to hold a charge I may fix it right. However there is nothing more permanent than a temporary fix that works.
This may be an option if you don't want to replace the dryer:
https://www.canadiantire.ca/en/pdp/red-tek-dry12-a-c-dehydration-treatment-4-oz-0146134p.html?loc=plp it looks like it might be a smart choice, maybe even in addition to a new dryer I'm not sure.