@Wayne-TP 

I have 2 C425's and both are now doing it. Currently one is showing offline the other just won't connect. The one that won't connect is attached to the network the other is not on the network.

i have a third Tapo camera on the same network that is fine, surely a cloud connection error would affect them all?

I have them on a dedicated IOT network so it is hard to check if I can see them locally but this kinda defeats the object of having them.

Tapo customer services are quite hard to deal with but if they won't work I nedd to return them and think about another brand.

  @Wayne-TP 

I mean - stability of firmware is a issue  ? 

I have 2 x c425 

d235 doorbell

2 x c500

And older c200 c100 

and sometimes without any issue are WiFi connection on cam or doorbell down, ping has answer from cams , app say  camera is offline. 
 

distance to router or repeater 10m 

I use small Linux server / monitor to control offline time .

ping camera -  ok

ping cloud server - ok

login to camera  / fails 

cloud answer over ping in this time without losing connection 
 

local hub200 has recorded  in some  time some video