Toddler is suddenly terrified of carseat

My 2yro has suddenly become terrified of her carseat.

It started on Friday. She was fine in the morning going to daycare, but when I picked her up at 4pm, she refused to let me buckle her. It took 1.5hrs of standing in the pouring rain on the street to get her calm enough to buckle up.

It wasn’t a tantrum because she didn’t want to leave. It was pure terror of the buckle.

For the last little while, she’s been saying it hurts as soon as we buckle her up. But kissing it better and pretending to loosen it settles her.

I moved the crotch buckle thinking that might have been where it hurts.

I haven’t been able to get her in since. I can’t wrestle her into it because she’s stiff as a board or pushes up to hover her bum in the air.

Any advice? She’s still rearfacing.