Are you sure that this would ever have worked?
I think that you'd need Hong Kong / China and Portugal to be added to Singapore's list of VTL countries, unless you are fine to spend your time in Singapore in quarantine.
On top of that, also your flight from HKG to SIN has to become a designated VTL flight. (Origin country = VTL country is not the same as your flight being a VTL flight)
Sounds risky to me to book something like that, so I'm not even sure if I'd wait before taking a refund.