i don’t know the full details of the XP calibration but it has something to do with players and the consistency, time and concurrent players.
I have a map that was calibrated and then the player base fell off somewhat to below the target i assume and it then went back into re-calibrating.
When it picks up above the threshold i then would assume it will go back into calibrated bracket.
I don’t think they is any issue or error and it is a simple fact that you have not made the threshold currently. If you keep working on your map and pushing updates ect I’m sure you will get calibrated at some point.