I just had this happen to me -- it turns out that there are 2 versions of Homelink -- Homelink V3 (HL3) and Homelink V4 (HL4).
Older HL3 garage door openers have a white antenna wire and white learn button. If you have a newer garage door opener with a yellow antenna and/or yellow learn button, you have HL4 and you need a HL4 compatible mirror or you need to buy a repeater kit from Homelink to make your HL3 mirror work with an HL4 opener.
To check your mirror, look at the FCC stamp on the back and see if it says HL3 or HL4.
