Can't open Excel files directly from Windows Explorer

I have just had my work computer "upgraded" with Office 365 (as ordered from the company IT-dept.) and had to spend a lot of time in the attempt to get things up and running again. This is really a pain in the you-know-what, but I am making progress - slowly.

One problem keeps bothering me:
Before Office 365 it was possible to double click on a file in Windows Explorer and then Excel started up with that particular file.
With Office 365 the double click only starts up Excel and that is not even with an empty sheet - it is completly blank except for the toolbar. I then have to click file - open - browse - etc. and click myself all the way to the particuar folder and file that I want to open. A lot of extra clicks that weren't necessary before.

Of course Microsoft will tell you that it's a feature and not a fault, but I would really like to be able to operate as before - it was much quicker and easier.

Does anyone know how to circumvent this "feature"?

Just got this tip that restored things (for the time being). Perhaps it wasn't a feature after all:
Control Panel - Programs - Uninstall a Program - Microsoft Office 365... - Change - Quick Repair