The SQL Server Network Interface library could not deregister the Service Principal Name
I ran in to same issue and I wander for about hours to fix it, finally I ended up repairing the existing database server 2016. 

download SQL Server Installation setup package from this link:
SQL Server 2016_x64_ENU
Go to setup.exe >> Maintenance >> Repair

While repairing, error prompted saying it could not restart the servers, yu can cancel that and let the repair finish. Once finished, start the SQL Servers

Right click on start and go to Computer Management >> Services and Applications >> SQL Server Configuration Manager >> SQL Server Services >> right click on all the servers and hit on start.

This fixed my issue and was back on track. I am still looking for a better answer on why or what can cause that but for now, here's the fix!

Good luck guys!