UpdateUptimeRegKey: Operating system error 5(Access is denied.)

This is because the user account that the SQL Server service is running on is not authorized in the MSSQL Registry files.

Solution

-> Run -> Regedit
-> HKEY_LOCAL_MACHINE
-> SOFTWARE
-> Microsoft
-> Microsoft SQL Server

Right-click on the corresponding instance Name, grant Full Control authorization to the MSSQL Service account from the permissions tab. The problem will be solved.

Note: If Instance has been upgraded before, the Microsoft SQL Server folder will have reg keys for multiple versions. If you grant authorization to the keys of the different version, the error will continue and you must grant full control on the correct file.