Are you turning it the right way?
I’m asking because I’ve seen circumstances where everyone was convinced that it needed to go one way, but many expensive hours later were proven to be wrong.
Also, is there something jammed in the pipe, like say roots or a snake?
Consider that any gift with a monetary value is likely something that they will need to report.
Sending two cards, one to them and one to their boss is one way to show your appreciation.
If you’re not sure about their boss, send the second card higher up the chain.