So we had two different sites with the Backup Option missing.
For the First site we eventually Ran through all updates, re-installs etc.. and found that the entry was missing .. run > regedit > \HKEY_CURRENT_USER\Software\Microsoft\OneDrive\EnableMove=1
Second site had a fairly secure environment setup and our hardware firewall was blocking access to certain MS services.
We temporary whitelisted the device on the firewall and BOOM! Immediately OD updated and the tab was visible.
