Need help programming chamberlain garage door opener replacement KLIK3U-BK
I had same issue, trying to program to a Liftmaster. Here's what worked for me:

Liftmaster: Press learn button.
Klik3U: Press programming button unitl LED solid BLue.
Press-release desired button on klik3u until Lifmaster lights blink.
Press Klik3U programming button to turn off programming mode.
Done.

I had to press the target button 8 times...hope that helps.