Phone Validation message/calls

United seems to have changes their app/website to use verification codes via email/phone (instead of relying solely on the registered questions/answers)

But I have problems receiving the phone # validation via Text or even a call.

This is with a Singapore phone on the Simba network.
I tried first while in Malaysia and thought maybe it was because it failed roaming, but
even now that I am back in SG this fails.

Has anyone else experienced problems with
- phone number validation in general (no SMS/text received, no phone calls received)
- in Singapore
- using a SIngapore #
- using a Simba number?

Thanks Mathias