Sebo Airbelt K1 vacuum (Dorridge B93)

Fair condition with good motor and the main suction hose and carpet tool (have mislaid the one that clips to the front but will hopefully find it before collection!) it’s working but, before I posted I opened it to check there wasn’t a full bag in there and now can’t close it again I don’t understand why. So if anyone has the knack or for spares