I use Viber on my Xiaomi Redmi Note 9 phone. 4 days ago i bought Lenovo tablet M8 and installed Viber app there. I was asked for authentication from my phone and so i did. When i switched off my tablet and opened Viber on my phone, i was asked to register, authenticate etc. on my phone. I did all that again but I lost some messages because the saved log, was from some hours ago. When i tried to open Viber again on my tablet, i faced again the same problems, register, authenticate, get codes via sms etc.
I changed the dpi on my tablet to 220dpi, in order to be recognized, as a secondary device as a user from here who faced the same problem with a Samsung tablet did, but it didn't work for me.
After entering and verifying my phone number on the tablet, i don't get the message to scan a QR Code, but i am automatically logged in and just get an email to confirm my e-mail.
I've contacted viber support and waiting for an answer.
I would also like to inform you, that i used to use Viber app on my previous phone, Xiaomi Redmi Note 6 pro, my previous Lenovo tablet and on my desktop Windows PC, without any of these problems for years.
P.S.: My tablet is WiFi only.