Meeting room declined

Question

I set up a standing meeting and scheduled a room back in Feb. The room accepted the invite. Then, in May I added another person to the original invite and sent the update. I did not change the room, date or time. I only added another person to the invite. Next, I received an email stating that the room declined the invite. When I checked with the office admin, she stated that the room declined because someone else was booked for that room. I'm not sure how that person would be able to book the room that I had already booked.