These Settings must be properly configured to keep Mobile Tracker Free working.
1) Settings => Battery => Battery saver => Power-saving exceptions => APPS => "Wi-Fi" => Turn ON
2) Settings => Battery => Stamina mode & Ultra Stamina mode => Turn OFF
3) Settings => Network & Internet => Data usage => Data saver => Turn OFF
4) Settings => Apps & notifications => App info – All apps => Wi-Fi => Data usage => Background data & Unrestricted data usage => Turn ON