Excel 2016 opening Multiple instances

[legento]

Hi,

I'm hoping for some help.

I am using excel 2016 and windows 10. I have a number of excel files on dropbox which consolidate into a file. The issue that I am having is that when I open the files some are being opened in a separate instance and I have no idea why.

The ignore other applications... that use DDE is unticked.

I have googled endlessly but I cant seem to find any solution.

Any assistance would be appreciated.

Thanks.