Now I really hope I have found this page 2.5 hrs ago, so that I don't have to waist my time troubleshoot and write up below email which I just sent out 10 min ago.
"I received a pop up message on my iPhone says the device is offline.
I went to garage and see the device is in yellow color.
I then checked on your website for possible solution, and it says to reset the device.
I did that, and filled in the password for the Wifi, but it still doesn't work.
I went one more step ahead, and deleted it from the app, and re-add it in following the instructions. still no luck.
double-checked from the router, that ping the IP address of the controller, it is reachable.
more troubleshooting - removed the tailwind app from my iPhone, and reinstalled it.
When I try to log in the app with my account(my email address), I got "Hmmm...the network connection seems to be down.
To isolate the problem from my home network, I disconnect my iPhone's wifi and only use the 4G network, and the same result.
Next I did was to click on reset my account password, and it gives me the same msg 'network connection seems to be down'.
Now I'm convinced that the issue is your server. it must be down."