What doesn't work:
- Going to Settings / More networks / Mobile networks / Network operators and
- Trying to connect manually to T-Mobile
- Setting to manual selection, then back to automatic selection
- Going to the Wind SIM toolkit and trying anything there
- Shutting down for some arbitrary interval (i.e. 30 seconds) then restarting
- Removing and replacing the SIM and restarting
- Having Wind turn USA roaming off and on again
No idea why this would work, but it did.
It might even stay connected if you then return "Network mode" to "WCDMA/GSM (auto connect). But I don't know if the original connection problem will re-occur the next time with this setting, or not.