Cannot drag web parts

I've recently faced with this problem. My solution is so;

1. Open the page in edit mode
2. Edit the webpart which you want to move
3. On the webpart properties section (which is on the top right of the page) Expand "Layout" section
4. On Layout section, there is two option
5. First one Zone selection. If you want to move the webpart to the different zone, select the desired zone
6. The second one is Zone Index. Use this if you want to change the order of webpart. For example you have two or more webpart in one zone. So you could change the webpart order