My Google Home Action do not sync device

I created a Google Home Action, and provided fullfillment, but after OAuth completed, my fullfillment do not receive device sync request, anyone can help me?

try double checking all of the steps again to make sure you did not miss a character, some of the URL’s require a trailing / so its best you double and triple check everything since it is easy to miss something due to the sheer amount of things to be done.