I'm new to the forum and have just received my JXD S7300 in the post today!
It's a great bit of kit but there seems to be an issue in that every time I re-arrange the apps and set up my wi-fi connection etc., I turn off the machine, the next time I turn it on everything is as it originally was.
I have literally started the machine up out of the box and not downloaded/updated any firmware but I thought that this would be okay still.
I've had exactly the same issue yesterday, but buyed my JXD S7300B a month ago. Just ran it... ZONK! Where are my nice, very important apps? Where's my desktop?! Also Google Play didn't work, just kept showing "Downloading...". The only way to fix it (that i've found) is factory reset. Completely turn off Your JXD, and turn it on with Volume "+" button. Some sort of Recovery Menu will show. In it, arrow down to something named like "Factory/data restore", probably the third option and press Your power button. Now, arrow down to "YES" and press Your power button again. Here, wait for the factory reset to go. When it's done, You will be moved back to Recovery Menu - Here make sure You're on the first option named somehow like "Reboot the machine" and press Your power button. Shouldn't happen again. And remember, for the next times because it could "go back" - There are two kinds of people. Those that do backups and those that will do. Sorry for bad English, i am from Poland. Good luck!