The ethernet cable may be the culprit. If it has Copper Clad aluminum conductors or just smaller gauge copper conductors the ethernet cable may lose a lot of the output power from your switch before it makes its way to the AP, especially if it is a long cable run. Great video below from Lawrence Systems with an engineer that works on the Cat5e,cat6 and Cat8 standards as well as POE. Cat7 is not recognized in the US and that is part of why so many Amazons sellers advertise cheap Cat 7 cables and they often underperform.
Go to the 17:30 minute mark for the POE discussion.
https://youtu.be/kNa_IdfivKs