What stops Range("B:HZ").EntireColumn.Hidden = True working

[Tiger20]

I have this code that has been working that now stops with the message - Unable to set the Hidden property of the Range class.
Sheet is unprotected at the time.

Please Login or Register  to view this content.

It stops on that line.
If I set the sheet up with columns hidden and add in the same line above this line except for False, it un-hides the columns and still stops on the True line.

A new blank workbook with the same code lines works OK
What are the things I should be checking for?

[Tiger20]

Problem received a better message when manually hiding in further testing.
Message "Cannot shift objects off sheet"