https://community.tp-link.com/en/smart-home/forum/topic/852764
https://community.tp-link.com/en/smart-home/forum/topic/852558
https://community.tp-link.com/en/smart-home/forum/topic/816658

I'm having the same problem. I'm in Australia on the Optus NBN network. 

Seems there are multiple threads about Optus customers - I suspect Optus has mass-deployed a router update which has somehow disabled Tapo camera connectivity. 

  @Plew 

Is there a solution? I'm also with Optus NBN. But I don't know if it's an issue with Optus or Tapo. Who should I contact?

  @Brian_Chen I feel it is Optus - the firmware on a number of my Tapo products, smart powerpoints in particular has not changed. I suspect Optus have changed something on incoming connections - I am trying their tech support at the moment - which can be hit and miss - will loop back here if I get any info

  @StuartF I am also on Optus. This problem was rabid for a couple of months earlier this year. I GUARANTEE IT IS A TAPO FAULT. i THINK IT IS WHEN THEY MAKE A CHANGE TO THEIR SOFTWARE OR SERVERS AND STUFF IT UP. The quality of their staff is VERY suspect. I have a smart home with over 50 different brands of smart devices. The only one that always has these outages is the Tapo devices. I have 3 cameras, 6 Led strips and some switches and they all become unreachable either in app or via Alexa. If it was an Optus problem then some other devices would act up but nothing does just the Tapo. I am going to have to start a "DO NOT BUY TAPO" campaign as this is unacceptable from a company who purports to be an industry leader. I am now so sick of this same problem happening over and over again. They NEVER update you when they solve the problem as they do not want to accept it was them. Their tech help has been absolutely useless in the past with this issue. They give you the standard old, re-boot, re- install...none of that works. You just have to wait until they get so many complaints they actually try to fix it. Frustrating like hell as it happens again and again! The only solution, I am going to replace every Tapo device in my smart home and bin them....good luck for you, hope it sorts out quicker this time.

  @Brian_Chen I am also on Optus. This problem was rabid for a couple of months earlier this year. I GUARANTEE IT IS A TAPO FAULT. i THINK IT IS WHEN THEY MAKE A CHANGE TO THEIR SOFTWARE OR SERVERS AND STUFF IT UP. The quality of their staff is VERY suspect. I have a smart home with over 50 different brands of smart devices. The only one that always has these outages is the Tapo devices. I have 3 cameras, 6 Led strips and some switches and they all become unreachable either in app or via Alexa. If it was an Optus problem then some other devices would act up but nothing does just the Tapo. I am going to have to start a "DO NOT BUY TAPO" campaign as this is unacceptable from a company who purports to be an industry leader. I am now so sick of this same problem happening over and over again. They NEVER update you when they solve the problem as they do not want to accept it was them. Their tech help has been absolutely useless in the past with this issue. They give you the standard old, re-boot, re- install...none of that works. You just have to wait until they get so many complaints they actually try to fix it. Frustrating like hell as it happens again and again! The only solution, I am going to replace every Tapo device in my smart home and bin them....good luck for you, hope it sorts out quicker this time.

  @Plew I am also on Optus. This problem was rabid for a couple of months earlier this year. I GUARANTEE IT IS A TAPO FAULT. i THINK IT IS WHEN THEY MAKE A CHANGE TO THEIR SOFTWARE OR SERVERS AND STUFF IT UP. The quality of their staff is VERY suspect. I have a smart home with over 50 different brands of smart devices. The only one that always has these outages is the Tapo devices. I have 3 cameras, 6 Led strips and some switches and they all become unreachable either in app or via Alexa. If it was an Optus problem then some other devices would act up but nothing does just the Tapo. I am going to have to start a "DO NOT BUY TAPO" campaign as this is unacceptable from a company who purports to be an industry leader. I am now so sick of this same problem happening over and over again. They NEVER update you when they solve the problem as they do not want to accept it was them. Their tech help has been absolutely useless in the past with this issue. They give you the standard old, re-boot, re- install...none of that works. You just have to wait until they get so many complaints they actually try to fix it. Frustrating like hell as it happens again and again! The only solution, I am going to replace every Tapo device in my smart home and bin them....good luck for you, hope it sorts out quicker this time.

  @KennyM1955 this is the first time I have had this issue and have 3 mains power cameras, 1 solar camera, 1 doorbell cam, 9 smart plugs, 3 smart bulbs, 1 smart hub + sensor. All are functioning OK as long as I am on wifi - so it feels like an incoming connection issue at the modem level. It could be that Tapo have changed something that is being blocked by the modem, or Optus have changed something. Really frustrating having all this gear that is only partially functional right now.