Firstly I had working custom subdomain for my appservice.
Then I bought SSL wildcard Certificate and then generated pfx file with password. Next I uploaded certificate using Upload Certificate under Private Key Certificates. Certificate has Health Status = Healthy.
Finally, under binding tab I added TLS/SSL binging for my custom domain, choosen this certificate and its type = SNI SSL. Everything seems to be fine, undet custom domain there is SSL State = Secure and SSL Binding = SNI SSL.
When I go to my website - there is no information about any certificates. I also tried the same with Create App Service Managed Certificate - the same effect, status Healthy, but certificate does not appear on the browser.