I've not had any problems with RMSD recently (either outgoing or incoming). In my experience RM have focussed resources on RMSD to ensure that it keeps on working.
The chances are that your item is still in the system and will emerge eventually. Sometimes things go wrong, even with RMSD.
RM considers a RMSD item officially lost if it hasn't turned up anywhere after 5 working days after its due date[1]. If and when that timeout expires then I guess it will be time to report it to RM so they can search for it and put in a claim with Parcelpro.
Footnote:-
1: https://www.royalmail.com/retail-com...on-policy-loss