Do you have any issues receiving calls in other countries? This is going to sound sort of silly, but you'd be surprised how often we see it, do you happen to know if there may be an international call blocking enabled on your account by accident?
Hey, magenta4905010 -- thanks for posting; I can see how this is inconvenient, to say the least.
Since it sounds like you've checked all the settings that can be reviewed on your end; in this situation I would recommend reaching out to our international roamer's Care team and having us take a look at your call forwarding settings. Maybe we could test extending the length of time/rings before the call is forwarded to VM? If that's not effective, the next step would be filing a ticket for this issue -- our team will just need to make sure we file it under the Roaming category.
Call while roaming internationally: +1-505-998-3793