For what it's worth: https://instagram.apk.cafe/prestigio/muze-b7 says it's meant for your phone so should work.
If no luck, go back to factory conditions and start all over to see if you can get it working with the standard instagram app.
If still no luck, either something is wrong with the phone (such as having Marshmallow only, or an hardware issue), or it isn't a quality phone at all.