Is it possible for none of the AirPod Pro ear tips to pass the fit test?

Very possible.

My left ear never passes the ear tip fit test with any of the supplied ear tips. I just think my ear opening is a little different than that of my right ear.

However, I really can tell no difference at all in sound our seal vs. the right ear when I'm using them. I finally just decided that the test is far from perfect. It's just sort of a guide.

I'm actually hoping that Apple takes an entirely different approach to ear tips with the next version of the Airpods Pro. I would like to see them employ the custom mold approach of Ultimate Ears, whereby the user takes the moldable material and light helps to set the fit for each ear. There's got to be a way for Apple to really solve this issue. The moldable material doesn't need to be huge. I'm sure there's a way to do this while still keeping the size reasonably small for the charging case. There's a solution to virtually every problem and Apple is capable of solving this one.

https://www.youtube.com/watch?v=BacAqyCXaz4

Yes, it is possible that any/all of the provided ear tips will not pass the fit test. This could be true either with new AirPods or with used ones. The former would be, most likely, that not all ears are alike or have the same size openings. The latter would be that they have become "misshaped" over time and no longer fit properly. This would be true of any in-ear buds, regardless of the manufacturer.

Try the Comply 2.0 foam tips.

My only recommendations would be, in addition to getting Apple replacement ear tips, would be to shop around for other third-party offerings. It will come down to the actual fit and comfort, especially if you need to use ear buds for an extended period of time.

The other would be to try other manufacturers' ear buds. I don't have the AirPods Pro, just the AirPods, but I have tried others. One of those I really liked is from Bose ... but again, this really comes down to personal preference.