Not implying you did it wrong but here’s how I do it: Use some light oil or even spit (my method) on the nubs to ease pull through, carefully grab hold with some pliers and gently (just enough to hold and no more) pull and wiggle the nub in a back and forth, side to side motion as you gently pull till it’s seated. Warming the seal a little makes it more pliable before hand. Just don’t squeeze or pull hard. I’m a proponent of deburring the holes in the pan so they don’t cut the rubber.