Error 'The file format and extension of 'Access Office Integration Excel Functions.xll' don't match' occurs because the bit version of the Excel Functions is different from the bit version of Excel. This example assumes Excel Functions 64bit has been added to Excel, but Excel is 32-bit. To get rid of this message:
Check the bit version of Office by opening Excel, and select File, Accounts then About Excel.
At the top of the window, the end of the first line, there should be either a 32 or 64 bit. In this example it will be 32 bit.
Within Excel, select File, Options.
Select Add-ins.
Use the Manage drop-down and select Excel Add-ins and click Go... .
Highlight Access Office Integration Excel Functions 64Bit, untick the check box, or on the right hand side, click Remove.
Click Browse... . A File Explorer window opens.
Navigate to the installation files for AOI, likely to be C:\Program Files (x86)\Access Applications\Access Office Integration (Client) <version>. In this location there will be 2 files called Access Office Integration Excel Functions, a 64bit one and the other is 32bit.
In this example, double-click the file Access Office Integration Excel Functions, which is the 32bit one.