The additional information is helpful (always good to supply all information). When you reserve on another carrier, in this case SQ, under IATA convention, they have 72 hours to confirm. While this is antiquated and should no longer be necessary, it remains. Some carriers just take more time and sometimes, it takes longer than 72 hours.

A call to the ticketing carrier, in this case, UA can help to force the ticket and that's what you did.

The answer remains that you need not call in and sooner or later your reservation should ticket. But, given that you are stuck with the vagaries of another carrier, if you don't see the e-ticket receipt, call.

As to the email to MP, you got the correct answer. They don't ticket. Never have. As a suggestion, emails are fine with CS issues. But, I would never use email to accomplish on-the-spot things such as ticketing. In this case, if something was wrong and SQ sold the seats, using up available award inventory, OP would have been SOL.