I am having issues with accessing the .xlsx data I use with my mail merge document.

When I open the document, I am greeting with ...

"Opening this document will run the following SQL command:
SELECT * FROM 'DATA$' WHERE 'TYPE' = 'FR'
Data from your database will be placed in the document. Do you want to continue?"

On selecting yes I get ...

"Error has occured: Class not registered."

I press OK and get this dialogue:

"FR15NG.docx" is a mail merge main document. Word cannot find its data source, U:\Education\....\Dates\Data\May-25 (Sat) schedule_5.xlsx

I press the FIND DATA SOURCE button, and the Select Data Source dialogue open. It's source directory is defaulted to "C:\Users\me\Documents\My Data Sources" and lists two .odc file.

The File Name is populated with "May-25 (Sat) schedule_5".

I change the file type to .xlsx and navigate to and select the source file from it's directory. (The file exists where it is supposed to be!), and press OPEN.

The Select Table dialogue opens up. in the window I would expect to see the worksheet DATA (the source of the mail merge data 'DATA$'), it is empty. The workbook field is populated with "U:\Education\Schools\School Admin\Timetables\Dates\DATA.xls"

I have no idea what is going on as DATA.xls is not a workbook, and not the workbook I referenced to find the data.

Is anyone able to tell me what has gone wrong? Everything worked as expected for months before today. Last night the IT department did some things to my computer, including the removal of Office 2010 from it as Office 2016 was also installed. So, I wonder if that is a significant contributing factor.