Keyboard letter T not working

I have an Apple Keyboard (US English, A1255) that came with my iMac (2009).

Now the letter "t" is not working anymore.

To distinguish whether it is a hardware or software problem I did the following tests:

1. I typed the letter "t" in another user account ("t" is not typing)

2. I checked whether typing the letter "t" would show in the keyboard viewer (doesn't show)

3. I connected another bluetooth keyboard ("t" is typing)

So, I am pretty sure that it is a hardware problem.

I removed the plastic letter button to see whether there is a mechanical issue. I does not look like a mechanical problem. I also did not pour any liquids over the keyboard. It was never wet.

Questions:

Does anybody know whether there is a way to fix the broken letter?

Is there a way to remove the white cover at the bottom of the keyboard? Perhaps I can see from there what is wrong.