Well, I am starting another one thread as there is no solution so far provided from the experts. 

After installing a new router at my home, I had to change the Wi-Fi password for the NC450. 

I did it via WPS button method, all set - all good. 

After trying to login to the TP-Link app (camera app) it keeps me asking for the password. 

admin password has no success. 

I have done so far almost 500 hard resets for the camera with the rear button, same story. 

You experts from the TP-LINK company, there is no solution for this major problem? 

My very next step if there is no solution to this problem, which is major and there are so many cameras affected, will be posts to X, revealing your inability to help your customers.