Airpods Pro 3 don't fit (pass the fit test) with any tip

Return them for a refund.

If purchased from Apple, you have 14 days to return them.

I've had the same problem with only the left AirPod from the original AirPods to the latest AirPods Pro 3, which I recently received. With each generation of AirPods I find I have to use the largest tips to achieve an acceptable seal. The AirPods Pro 3 left AirPod can be made to achieve a good seal but it quickly loosens, especially if I open my mouth (eat or speak) and it has fallen out several times. I'm now looking into 3rd party tips, and wish I didn't have to. The only alternative I found was a silicone device that slipped on the body of the AirPod and had a protruding curved piece that would fit into the curvature of my ear. That held the left one in, although it was still somewhat loose, but it also had to be taken off each time the AirPod had to go back into the case.