It's in a compressed file so you have to extract first.
Viewing post in Stop Master: The Time Freeze Visitor comments
Not sure what the deal is. Could be a security issue with the phone thinking there is a virus. Also a lack of space/memory dependent on the phone you're using. For unofficial games and apps I use Aloha to download and install. After the initial give it permission I havent had any problems. That could be something to try out as well.