It is compatible though it is an older mirror.
See:
https://www.ecstuning.com/Search/Sit...79541/ES88201/
It has been superseded by other mirrors such as 51169159090... which was superseded by this one....
https://www.ecstuning.com/b-genuine-...r/51169159121/
And the 51169159121 is specifically compatible with your E90.
The wiring is the same for all three mirrors, since one could not supersede the other if not.
See:
http://parts.bmwofsouthatlanta.com/p...169159121.html
That is how I found a compatible mirror for my car at a decent price on Ebay.... I chased down the part number progression.
The one I purchased was for an X5. It came off a wrecked car and the car wrecking company posted the wrong part numbers.
I referred to the actual photographs to determine it was in my list of superseded mirrors... it worked fine after installing.
For more info you can search for any of the other parts numbers listed at the ECSTuning web site above.
How did you "Test" the mirror?
Does the LED Compass light up?
Start by getting everything other than FLA working.
Did you also VO code your car for the new mirror and code/reset the FZD module to get it to recognize the new type of mirror?