"Confirm your identity" on fb marketplace after Tahoe update

I've had two items listed on marktplace for some time, but they're no longer active. Out of the blue, fb is asking me to confirm my identity for marketplace, which I tried to do. It asked for my cell phone no., which it already had, and then I clicked 'send code.' It did not send a code; instead it said that I should give my Australian phone no. I'm in Canada; never been to Australia. The only thing that's different is the Tahoe update. Anybody else?