Observability Fundamentals lab 2. create nginx dashboard. error Request must contain a kbn-xsrf header

When i follow steps from Official Elastic Training Observability Fundamentals and trying create nginx dashboard i gon an error {"statusCode":400,"error":"Bad Request","message":"Request must contain a kbn-xsrf header."}. Video with this error https://youtu.be/L18sIq72_-4

I triyed do the same things in incognito mode without adblock and got the same result. For solve this problem, i did this steps in linux. I assume, that the problem was in browser settings. But i don't know what exaclu was a root of the problem. So if you encountered with this problem try it again in other browser.