Cannot set default SMS gateway for domain

Version 10.6.23

I’ve successfully configured an SMS gateway in the global settings, but upon trying to choose that as the default gateway in Manage Domains / Account Defaults / Quotas and Restrictions / Account Security it keeps reverting to “no connector” no matter how many times I choose the one I created and save the configuration.

Then when I try to setup a 2nd factor using SMS, an error to the effect of “no sms provider available for user” shows up in the log.

Anyone else experiencing this or something similar?