I am trying to book the following ticket: SID-NSI 24 September Which consists of AT587 and AT507 with transit in Casablanca (CMN))

I have been trying to book this ticket for a week. I have spoken to the Royal Air Maroc call centre and they gave up and said "go see a travel agent".

I thought it might be that the AT587 which originates at RAI, might not take on passengers at the technical stop of SID. But I can book the same flight from SID to CMN without issue.

I have reached my limit of travel knowledge and do not know what to do next.