Saeco GranBaristo Avanti brew unit not ejecting puck

Problem : Beloved Saeco GranBaristo espresso coffee machine is not ejecting the coffee grounds / puck from the brew unit.

Coffee machine makes coffee - but the coffee grounds remain in the brew group. Yesterday the used grounds were a little watery, today they formed a solid puck.... but in all cases, they are not getting dumped into the dump box.

Any ideas on why this may be?

This started after a descaling cycle.