Whenever I try to download an app in the Google Play Store on my Samsung Galaxy S3, it keeps saying "package file invalid" and won't let me download anything. The message also has a triangle with a ! inside it.
Try downloading via WIFI.
I had this issue recently, same phone. Tried a few times; both on PC and on the device itself each failed. I realized WiFi was off (mobile data only). I turned WiFi on and the file downloaded first go.
- Log into Google Play Store (via browser)
- Scroll to the bottom of the page & Locate "My Orders & Settings"
- Click on the Settings Tab
- Assign a "Nickname" to your phone
- Check "Shown in Menus"
- Save settings
- Return to the Play Store and download Apps.
This worked for me.