Ran into this today, but luckily there is a quick fix (at least for me)! I created a new B2ms VM running Server 2016 Datacenter but as soon as I booted it up, I saw there was an activation error. I tried to run the activation tool but no dice.
I found this help doc which provided this Powershell one-liner to add Azure’s KMS licensing servers just in case they were missed:
Invoke-Expression "$env:windir\system32\cscript.exe $env:windir\system32\slmgr.vbs /skms kms.core.windows.net:1688"
I re-ran the licensing troubleshooter and voila, I was activated!