Play Protect acts like an antivirus app. Generally, it's a security app that scans your phone regularly for malicious and unsafe apps (including the apps you downloaded from Playstore and the ones you downloaded from other sites).

Recently, some couple of people laid a complain to me that they get "Blocked by Play Protect" error anytime they want to install third-party apps like Mobile Uncle, Lucky Patcher, and other apps that are not on Playstore.

Full tutorial can be found on the source link.

Source: https://www.entclassblog.com/2018/05/fix-blocked-by-play-protect.html

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Okay

johnrabbi:
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https://luckypatchergames.com/download-lucky-patcher-original/

Just download lucky patcher and fix the problem. Download link
https://apkzoo.com/lucky-patcher-app/