Hello, @marvinG 

May I know the model of your wifi router, does camera work remotely before? 

If your Tapo camera works fine when phone is connected to Home Wi-Fi, but goes Offline or Unreachable when phone is on mobile data, you could try some suggestions here: 

• Turn off or lower Modem/ router Firewall settings
• Check if there is any Advanced settings on router like access control/ parental control settings may affect the camera
• Change router's DNS to 8.8.8.8/ 8.8.4.4
• Reboot camera 
• Make sure camera is connected to router directly, not through other AP or Range extenders
• Make sure tapo firmware in tapo app and tapo APP version are both up to date 
• Try to use  3G/4G mobile data or connect phone to other outside Wi-F networks

If the same problem, please help collect the log of camera and share with us ,thanks~ 
How to get the logs of Tapo Camera: https://www.tp-link.com/support/faq/3151/
 

Hi @marvinG  , 

Connecting camera to router through Wi-Fi or Wired connection shouldn't make a difference on camera remote control.

You could factory reset camera, and hook up camera to router again, please select Ethernet (Wired) option when set up the camera in APP

How to reset: https://www.tp-link.com/support/faq/2705/

If the concern persists, may I know the model of router and your network map,e.g. router Archer C7 < Wireless> XX extender <Ethernet>Camera

Is there any extender or switch between router and camera? If possible, please share the log file of camera so we could analyze the possible cause, thank you.