RDB Merge Addin not recognising Excel files.

I have used the RDB Merge Addin for a few years now and never found an issue with it until recently.
Basically, I have a lot of xlsx workbooks (1000+) that I have created in VBA (by saving as) that are not recognised by the RDB Merge Add in.
When I select the folder, the RDB Merge Addin returns a message "No xlsx files were found". I have tried the other variations (xl? etc) but they return the same error message.
There are definitely xlsx files in the selected folder.

The files were created using this line of code:

Please Login or Register  to view this content.

Is there something missing from my code which is causing this issue?

Any assistance appreciated.
Thanks.

Thanks for the reply Pepe.

I emailed Ron at that email address about 3 months ago and unfortunately have not received a reply.