cannot enlarge photos since installing Sierra

I don't understand your response. I don't think I could have made it any clearer, but I'll repeat: Since I installed Sierra yesterday I cannot enlarge any photos in Apple Photos by double-clicking on them. You asked "what does happen," but the issue is not what does happen, but what does not happen. To repeat again, the photos simply do not enlarge as they are supposed to do when you double-click on them. It's really that simple.

It appears to be a Sierra compatibility issue with the Magic Mouse, perhaps Bluetooth related. Not my specific Magic Mouse, but evidently with all Magic Mice. Both of my Magic Mice do the same thing on both my iMac and my MBP, i.e. when I double-click on a photo in Apple Photos it does not enlarge/zoom in as is supposed to happen and did happen without failure until I installed Sierra. This is the only Magic Mouse abnormality I have discovered since my Sierra install.

My conclusion that we have a Sierra/Magic Mouse compatibility problem is based on the fact that I have used a USB plug-in Apple mouse, a USB plug-in MS mouse, and a wireless MS mouse that connects through a USB plug-in transceiver, and none of them has had this problem; they perform perfectly normally. Also, doing a Google search I discovered that others are having problems with their Magic Mice with Sierra, though not my specific problem. Example: professional users of Adobe products are having problems with their Magic Mice since upgrading to Sierra to the point that they cannot use the software productively.

I've parked my Magic Mice until this apparent bug is addressed and fixed.

Thanks for the suggestions. Tried both of them but neither fixed the problem.

I'm finding that our conclusion is correct that the fault lies in the Magic Mouse's compatibility with Sierra. I bought a MS Designer Bluetooth mouse to see if it would work. It works just fine, suggesting that it is not the Bluetooth per se, but the Magic Mouse's interface with Sierra via Bluetooth. Hopefully with more complaints someone at Apple will get to work to find a solution. Meantime I'm sticking with my new MS mouse which, btw, was a lot less expensive on Amazon than is the Magic Mouse. Doesn't have the trackpad-like functionality, but it does everything I ask of it.

Both of my Magic Mice are Model A 1296s. They're both still not enlarging images on either my iMac or MBP.