It seems like the Ooma moderators, that are also Ooma Engineers had been AWOL for some time, at least from the Ooma Forum.
This has helped other people in the past:
Access My Ooma https://my.ooma.com/blacklists and temporarily Disable both black lists, and click o Save.
Next access My Ooma https://my.ooma.com/privacy and temporarily disable Anonymous Call Block and click on Save.
Next remove power from your Ooma Telo for twenty minutes. At the end of the twenty minutes, repower the Ooma Telo. Test using your cell phone to call your Ooma one line number.
If you haven't do so already, be sure to report your problem to Ooma Customer Service:
Phone: 1-888-711-OOMA (6662)
Monday-Friday 7am-7pm PST
Saturday-Sunday 8am-5pm PST