have you tried different cables, different power adapters? does the power adapter and cable work with your other devices?
is it possible there's dust etc inside the port?
it's possible that all they did before was clean the port out with compressed air in a can or perhaps after disconnecting the battery to eliminate the risk of shorts may have used IPA to clean out the port carefully with something to probe it, if that is the cause then probably wanna invest in some plugs for the charging port, I have silicone ones for my devices and it's great for keeping dust and any accidental splashes from getting in the ports.