These Settings must be properly configured to keep CellTracker working.

• Settings => Dual SIM & Cellular Network => Using Wi-Fi and Cellular Network => « GPS » => Select ‘Wi-Fi and Mobile data’
• Settings => Dual SIM & Cellular Network => Data Saving => Turn OFF
• Settings => Security => Permissions => Apps => « GPS » => Allow All
• Settings => Battery => Power Saving Mode => Turn OFF
• Settings => Battery => Smart Power Saver => Turn OFF
• Settings => Battery => Power saver options => Sleep Standby Optimization => Turn OFF
• Settings => App Management => « GPS » => Data Usage Status => Network Permissions => Wi-Fi and Mobile Data
• Settings => App Management => « GPS » => Data Usage Status => Background data => Turn ON
• Settings => App Management => « GPS » => Data Usage Status => Unrestricted by “Data Saving” => Turn ON
• Settings => App Management => « GPS » => Power Saver => Allow Background Running => Turn ON
• Settings => App Management => « GPS » => Permissions => Allow All
• Settings => App Management => « GPS » => Auto Startup => Turn ON
• Settings => App Management => « GPS » => Floating Windows => Turn ON
• Settings => Device & Privacy => Location => Apps Using GPS in Background => « GPS » => Turn ON

Be careful, with ColorOS:

• During an audio recording, the notification bar will blink red to warn you that a recording is in progress. It is not possible to hide this, it is a security of the ColosOS system.