Although it is not quite the same, we had a similar situation. We asked for permission to leave the ship for 5 nights and travel on our own, rejoining the ship in another country later. We were immediately denied with no explanation other than a generic list of possible reasons. I called my travel agent and she called the deviation department or whatever it was called. The deviation was approved the next day and I received an email confirming it. Neither my travel agent or the person at Princess could figure out why it was rejected. If it is important to you I would at least ask your travel agent or whoever submitted the request to find out the reason. It’s possible because you would be checking in for the first time it really is denied, but I’d give it another try.
This happened within the last couple of weeks. It’s current.