FROM FLEXISPY SUPPORT!!!
"We're sorry to hear that you experienced an issue again.Please be informed that we just released the new version (3.5.7) yesterday. You may try this version, but unfortunately it might be detected again within a day or two. Please understand that the software might be detected by Play Protect again.Our engineer will release a real fix to this problem which will hide software at the installation process so it won't be detected by Play Protect after the installation. This release should be available on this Friday.
If by any chance software stops working again on the Target device, please be advised to wait for the real fix. You may lose tracking with the Target device for short time.
Once the real fix ready, you will see "Software update available" message inside your dashboard. The version number will NOT be 3.5.x anymore. It can be 3.6.x, 3.7 or 1.x (if we have to come up with a brand new product."