I don’t know.
Here’s another user with the same problem, and it hasn’t yet been resolved.
Waiting to see if it’s safe for them to try to force a degraded import with the other (“more recent”) TXG.
If that works, then it might be possible to do the same with you, and then it’s a matter of resilvering the pool back into a healthy state.
What caused this in the first place? I don’t know. It was noted that four different people seemed to have a similar issue of “pool cannot import with any version of TrueNAS anymore” after upgrading/sidegrading to 24.10 or 25.04.
You and @JGordonT are two of them. The other two have moved on, one of whom wiped and reused their drives, so there’s no way to diagnose any further.