I have seen issues with corrupted named ranges in various Excel versions. Could you try temporarily changing the name of the xlsm file in the export so that it creates a new one the first time it runs. Then try and run it again to see if it can append to the new version.
If everything is good with the new file, then please try to delete and recreate the named ranges.
Incidentally, to change the Excel file type from xlsx to xlsm. I believe you would need to change the file type drop down AND the file extension in the destination line.
I deleted the tab within the destination Excel file and allowed the Automator to create it. Afterwards, Automator worked perfectly by replacing the tab versus creating a new tab has it had been doing.
I believe that is what I'll do going forward.... If I want the Automator to append to a file, but replace a tab, I'll let it initially create the tab versus having it write-over a tab I've created. Automator sets up the table range and does the replace going forward perfectly.