Lately my 10/22 has been having difficulty firing.

At first, I thought it was bad ammo.  I'd pull the trigger, hear a click, and nothing would happen.  When I manually cycle the bolt, the round would fall out, and show that it had indeed been hit.

However, it is happening far to regularly now, and with different ammo.   I'm guessing that it just isn't hitting the rim hard enough.

Where should I start looking for the solution to make my plinker plink again?

Try cleaning your firing pin, or replacing it.  Don't get one of the titanium ones, I've heard they cause a lot of light strikes that won't fire.  Get a factory one and you'll be fine.

Have you recently removed the barrel? If so maybe you did not push the barrel far back enough.  If that's not it replace the firing pin. I had a bad firing once and the thing is the firing pin looked GOOD but it was not. Let us know if you get your 22 up and running.

Or maybe the barrel's v-block screws loosened up.