You have checked every possible setting for GPIB/IEEE in MET/CAL. You have verified that your GPIB interface "sees" your unit. You are still getting IEEE errors.
There are things that will give you MET/CAL errors that can only be identified with Trace mode.
To get into Trace mode you will need to log in to MET/CAL Editor. Trace is under the Debug menu.
You can see that Trace will help you identify communication errors for IEEE and RS-232, but also help you with ACC file errors.
To make Trace a useful tool, you will want to make sure that your Output window is visible. To make it visible if it is not already, click View>Output.
Now select Trace>IEEE-488 I/O
Once you have selected Trace and have started debugging, you can select Trace from the Output Window dropdown to see a character-by-character log of the communication going on between your computer and your IEEE devices.
When you have finished running Trace you can read the output and see if you can find the problems. Or you may want to copy and paste the results from the output file into a text document. You can send that document to firstname.lastname@example.org for additional assistance.