We’ve had a similar experience. Royal Mail tracking says our daughters birth cert was received on 7th Feb. System was not updated to say documents received until 25th Feb (14 working days later). It then stayed at documents received until Thursday 10th March where it’s said application being processed ever since. When I call they tell me they can’t tell me any further details as to when we can expect it. It’ll be 6 weeks on Monday since they got her birth cert.