LEDgardener

Just my opinion but tinning wires inside squeeze connectors is a bad idea. The tinning will compress and the wire can eventually work its way out. Ferrules are a much better option if sized correctly.

Elevator dude: that does look like a good option. I'll try with the solid core, and if that doesn't work out, I'll try ferrules.

About the parallel wiring, I assume the best way is to simply wire all the positive terminals together in a daisy-chain and connect to the positive terminal on the driver, and vice versa for the negatives?

looks like a high density strip light. this site maybe provide some idea on resolving your trouble. https://www.onlumi.com/led-light-strip-connector/

Teknik: I've now tried all 4 connectors on one board, and it's the same thing, so I think I'm just doing it wrong.

0 to 220: That makes sense. Should the insulated part of the wire also enter the hole?

Mine seems to be too thick for that. Would 20awg be the ideal wire?

I read in connection with poke-in connectors where someone recommended solid core wire.

Would 20awg solid core be better than 20awg stranded for this purpose?

Your problem is the stranded wire. If you go to solid core. Or tin the wire you'll be able to get them to go in no problem. I prefer the solid core because I hate tinning every wire end so it gets stiff.