Logs are filling with loads of errors.
Description: Failed to start tasks - database is not ready.
Failed to construct DatabaseContext object. Connection to database failed.
SQL connection failed, current user=Domain\ServerName$
SMP 8.0, 8.1, 8.5
The Altiris Client Task Data Loader Service account was changed from Local System to Network Service.
Change the Altiris Client Task Data Loader Service back to run as Local System. In addition, make sure other services are using correct domain accounts so it's possible for task service to impersonate the Altiris services account when necessary: