This is normal - SQ's systems generally is their downfall and causes way too many calls to their call centres precisely because they can't allow customers to self service. For example,
- when I click on Change Flights on some of my ticketed award bookings, I get a silly message that "MALMS not responding. If making changes to VTL flights, contact SQ" (yes, even though VTL has been defunct for months).
- when I want to add stopover to my roundtrip saver awards, the Add Stopover command is greyed out.

Looks like there's no other option but to endure a call...