M-Files ribbon in MS Excel (with a slight twist)

I've checked out an excel file and updated the content, per a recent revision request. Now, I want to add some properties from the metadata card, using the M-Files ribbon, but it's not currently available for this particular file?  I've looked in the Excel Add-ins, under Developer and there's no option there to enable it. Having successfully done this with MS Word files, in the past, I am curious if there's a "trick to the trade" for getting it to work in Excel?  Additionally, I'm wondering if the issue is the file I'm revising has had the Excel extension changed (it is no longer .xlsx since we use the content as a .exe file, once released). Any suggestions? For now, I'm manually adding the details to the footer, but would like to utilize the dynamic features the metadata cards allow.