SQL service account

The service account for SQL is generally domain\sqlservice or similar. You should not be using domain\Administrator as that is bad practice.

In order for this, (notionally) non-standard admin account to function, it should be also made a member of the local computer Administrators Group.

Event Log Errors in pairs like:

Login failed for user ''. The user is not associated with a trusted SQL Server connection. [CLIENT: ip address local host]

with

SSPI handshake failed with error code 0x8009030c while establishing a connection with integrated security; the connection has been closed. [CLIENT: ip address local host]

indicate that the service account is not authorised to access its own SQL server. Adding the domain\sqlservice account to the local administrators group should fix this error.