The OP is not asking which lounge can they access, but if they can access the lounge with an expired card.
Obviously, the official answer is no. In reality, however, it takes time for the new status to be reflected in the GDS/DCS even if you are flying with the same airline you have status with. It takes even longer for the new status to be seen by the OW members, up to 2-3 weeks in some cases.
In this particular case, if your enter the FFP into the booking before the status actually expires, I don't think the QR system will be quick enough to see that you lost status 3 days ago.
Would be grateful if you could let us know what happened at the end
