No application is accepted to be installed.

Please help.

I own AC700 and google account.
I intended to install google application from goole app store but no application was accepted.

1) Account setting was finished.
Favorites Bar shows my favorite web page set by my Windows PC Chrome browser.
2) Open new tab.
3) Tab shows "File Manager" and "Google App Store" icons.
4) Select "Google App Store"
5) Browser moves to Google App Store website.
6) Select any application on the site.
I tried "Gmail Offline", "youtube" and some other.
7) Small window opens and ask confirm installing.
8) Select "Yes"
9) Few seconds later, small window opens and says;
"Installing was failed. Extensions are not enabled."

I could not install any application or extension so far.
AC700 looks like web browsing PC...

Could someone know the reason and let me know how to resolve this problem?

Thank you in advance.​