Issues with Split Screen with El Capitan

I updated to El Capitan yesterday and enjoyed the split screen feature. This morning, however, I tried to utilize the feature again, but was unable to drag the window with the green button. When I click, hold, and try to drag, the window remains immobile. All other features seem to be working. I checked and confirmed that "Displays have separate spaces was selected. I have a 2010 13" Macbook Pro.

Any thoughts on how to troubleshoot this problem?

Thanks!