One condition that is required prior to testing is that key components are within predefined temperature ranges. If you have the proper password access to the F9 functions you can check the current operating temperatures of these components and identify which is out of range.
Generally, "REGULATING TEMP" is only displayed for a short time, perhaps 20 - 30 minutes if the instrument has been turned off.  If this display continues after a reasonable warm-up period, you should contact Technical Support for assistance.