APKPure Appを使用する
Instaweather Lollipop fixの旧いバージョンをダウンロードすることが可能
Instaweather temporary fix for Lollipop 5.0 users
This is Instaweather PRO edition for Android Lollipop early adopters fixing error -505 during App reinstallation. We will maintain this version until Google will release fix for certificate calculation bug.
Other option is to make factory reset, and instal standard version of Instaweather.
Confirmed it has been solved with 5.0.1 (verified with Nexus 9)