My SARH missiles won't lock on a target

Idk why, but since like a week ago my SARH missiles (R-3R) on a Mig21(R-13-300) just won’t lock on a target, radar locks, but missiles doesn’t. Can you help me out? What am I doing wrong?

There can be a few reasons for it. 1 is if don’t run missile selections it has a weird issue of not wanting to fire or work. So I make sure it is selected on a sarh missile. Next with sarh missiles like the r3r is you got to be at a certain angle like level flight and second high enough that it’ll not give up cause of ground clutter. I sorted it out by flying 2.5km up or even 3kms up. You can of course go higher. Next is target range so the radar won’t lock right away. You’ll have to wait for them to get into range and also keep in mind that you can’t be at alt but so does your enemy needs to be. They might not be at alt for your missile. Hope this helps.

We need a video of what you’re doing wrong