Hi there I have a similar problem as one mentioned in this issue:
I provide the link because it has a very useful video.
In my case what happens is that after using the + sign to access the upload image button, the finder opens normally and I choose my image file. How ever then nothing happens after that, no image is uploaded not even a div with no image. Just nothing happens. If I keep trying, then magically it will work, some times I have to try 4 times some times 60