Just looking at the instructions you wrote and comparing to the instructions on the Liftmaster in your picture (you can read them on the back of your unit) - there is one small discrepancy and some info that you did not state.
1: Did the LED turn on when you pressed that Learn button (YELLOW BUTTON ) ?
THE LED that should light is the one to the left of the Yellow Button (next
to the White Up/Down buttons).
2: Did you hold the button and wait for the LED to turn off?
Regardless of the fact it says to press and hold for 6 seconds, press
and hold (at least 6 seconds) watch the LED light up (YES lets hope it
does or maybe the button is not working or the LED is not working) and when > the LED is lit up wait until the LED turns off and then release the button.
Once that has been done exactly as specified As in the quote of step 2 (if that does not erase the codes), do the procedure again and then with out pressing any buttons or anything else unplug your Liftmaster for 1 minute, and then plug it back in.
P.S. I don't think your unit is fried, broke or otherwise. ...
EDIT 12/4/2017
If the Learn LED never lights when you press the LEARN button (and you know for sure the LED works) .. Then it could be something very simple - like your learn button is broken - but don't get anxiety over that - to repair that it could be very easy as sometimes these are plastic with an eraser like surface on the other end - when pushed the eraser like surface touches two copper traces of a printed circuit board (PCB) together to make contact.
TO FIX LEARN BUTTON : Clean Eraser like substance with alcohol (not rubbing as it has oil) , use a pencil eraser on the PCB copper traces underneath the button - then clean with alcohol - reassemble and test the switch. And of course the unit should be unplugged when you do this cleaning.
If the switch is not of the above mentioned type - but a board mounted switch You can also check the switch with the logic unit removed - perhaps a bad solder joint on the logic board.
If you should choose not to do those checks or just don't want to invest time in that - you can order a new logic board for the 8550 (I am not sure but I am guessing yours is similar to the 8550 or 8550W) guessing by the part number in your picture.
A Non WIFI unit is $88.00 and a WIFI unit is $140.00
This part replaces the following legacy #'s : 041D7356, 045DCCR, 045DCBR, 045DCCL, 045DCBL
045DCT is a Security+ 2.0® receiver logic board replacement kit. Compatible with various LiftMaster® DC chain and belt drive garage door openers; made after 2011. The unit will feature a yellow learn button. Check the manual for your specific model number before ordering to ensure compatibility.
Logic Board for WIFI is $140.00
Also if you are in the USA : Since you have to do this because someone stole your Remote Entry - Theft - Capital Loss - the possibility exists that if you itemize you could write off the expenses of repair as a loss. I know that is a tax tip and not a fix it tip but just thought I might include something that could be positive in a bad situation.
