That is a long time. You should definitely check they’ve actually got it in the system.
I worked somewhere where cheques are received/processed and I can tell you that after the various stages and checks that each credit goes through, a very small number of them are missing and turn up in the bin or in some random place due to human error (stuck to the envelope, or gone with the wind).
That’s not even taking into account all the letters that end up on a pavement or in a gutter from the postal system before it even arrives at the bank
Definitely chase that one up.