Your oem CMOS is faulty and that is why its not appearing in DM, I don't know what you did when you say "Tried adding an imaging device and then a generic camera in the device manager" as a USB camera will work 100% which I suggest that you add if you want a camera with your laptop.

Otherwise, you need to replace the oem CMOS and Dual Microphone Module with one of the AN515-41 oem CMOS and Dual Microphone Module below, which is a big job as you need to undo the screen bezel and insert one of these cameras:

CMOS and Dual Microphone Module

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@NeilSmith

We might have to do power drain test and bios defaults

I am really sorry for the inconvenience..   Let us do the basic steps first..

Doing the power drain and bios defaults will really help.  Kindly follow the steps given below:

Kindly go through the details from the link given below

https://community.acer.com/en/kb/articles/75-acer-internal-battery-reset

Turn off the laptop. Disconnect or unplug the charger cable, devices or any other cables connected to your laptop. Close your laptop. Turn it upside down.  On the bottom of the laptop, you can find a  pin hole. It is a tiny hole. You can a find a battery symbol indicator next to the hole. It is like a + and – sign symbol as though somebody is trying to shift the battery out. Insert the pin on to the hole for 30 seconds. Remove the pin. Flip the laptop. Connect the charger cable, turn on the computer.  Only on laptops where the battery is inbuilt you can find the battery reset hole on the back of laptop.

If you don’t find a pin hole on the back of laptop then you might be using removable battery. There is no need to unscrew anything to remove the battery.  Turn off the laptop. Disconnect or unplug the charger cable, devices and any other cables connected to your laptop. Close your laptop. Turn it upside down.  On the bottom of the laptop, please look at the top or bottom depending on the way you look at it. You can find a long door. It is a battery removable door.  Just below that you can find a latch.  If you move the latch you can remove the battery door. Once the battery is removed, flip the laptop. Open the top cover, press and hold the power button for 1 minute. Connect the battery back on the back of computer. Connect the charger cable back and then turn on the computer. 
 
If you don’t see a reset pin hole on the back of laptop or if you are not able to remove the battery (if it is inbuilt) then please unplug all the cables and devices out of laptop.   Hold the power button for 1 minute.  After releasing the button you should wait a while before plugging in power. Just because the button has been pressed doesn’t bleed off all the residual electricity on the motherboard. Wait 15-30 minutes before plugging in power. Then once power is connected wait for a full battery indication before turning the system on. That allows the battery to fully reset it’s internal statistics.

Connect all the cables back and restart the computer.  

While turning on the computer, tap f2. It will go to bios. Press f9 once. It will show load bios defaults with a yes or no popup. Press enter. Popup screen will disappear.  Press f10 once. It will show save changes popup with yes or no. Press enter. Computer will restart and it will load into windows.   
 
It should work fine..