Do you have much lightning in your vicinity? If so, the chip inside the camera or the POE port on your POE switch may have been damaged by ESD due to a nearby strike.
Have you tried another port on the switch?
Have you tried another Ethernet cable/ inspected the camera's pigtail connection for corrosion?
I see you are able to inspect the inside of the camera...any visible damage such as black areas or damaged traces? Any burnt smell?
P.S. - Welcome to IPCT !