I had this issue, too. It was vaused by clicking on the window handle. I heard a noise from the escaping air. When I clicked again, the window closed and pressure built up slowly. Not sure, if it realistic that a slightly open window prevents an entire A380 from pressuring up and then it takes minutes to build up the pressure again.
I had the same issue yesterday. What solved it for me was to go into my navigraph account, sign off all a220 connections and reconnect again later in the aircraft. At the same time I closed my vpn connection for the database update. One of these two measures was the magic bullet and I strongly believe it was signing off all related connections. Regards Rolf