This article applies to PRTG Network Monitor 12 or later
The Reason for ADO SQL Sensor Errors after Changing Service Account
If you have changed the service account of the PRTG Probe Service and then encounter stopped ADO SQL sensors, this problem is probably caused by the following:
There must not be set any TEMP or TMP environment variables for the user account the PRTG Probe Services uses.
If you log into the server running the service as a (local) user, take a look at the environment variables of the user. By default, TEMP and TMP variables are set which point to the user profile. But because the user profile will not be loaded automatically with the service login, PRTG’s requests to TEMP folders fail.
The OLE-DB driver creates a temporary file in the directory specified by one of these variables. If the directory does not exist nor has the permissions, then it will not work for a common user.