@shunsy 

first up, you would not hear a beeping sound from the tp products unless you are talking about the home products like a cam, speaker or vacuum robot. whatsoever that may come with a speaker. 

if you say the sound buzzing sound from the adapter, i buy that. you probably get a dead adapter or something shorts or burns inside of the adapter and it stops powering up the eap.

but beeping.. geez, I've seen a lot people saying this but i never really saw my clients showing me this. all of them turned out to be another device beeping. not the adapter nor the eap while they don't get speakers. only the pcb or some parts may buzz which depends on the scenario. buzzing sound on electronics, adapters or power outlets, can be considered normal. you need to seek help from the electrical technician to find out what's wrong. is that a part on the pcb that fails and causes the sound? The regular tech rep won't figure that out.

  @shunsy 

I think the OP meant *really* faint, like a POE circuit trying to power up it's main coil.  It's either power isn't getting there, or there is nothing to get to.

1. power up the unit with a different known good cable and the passive POE block that came with it (if you aren't already using it)

2. if you are already using the provided passive POE block, then use a different cable between the POE adapter and the AP

3. if that still doesn't work, it's either the AP or the POE block that is not working.  You can replace the POE block with another, or a standard POE or POE+ device.

4. if you still cannot get the AP to come back to live with a different cable and a different good POE injector, then it would tend to point to a failed AP.

If you have used cables fabricated on site, I'd say you might have a cable fault...try a cable tester if you have one.  Though, it could even be marginal/intermittent failure, where it works enough to light up the tester LED, but as soon as your start to draw real power for the AP, the connection breaks.