Redirect all HTTP requests to HTTPS automatically

Hello,

I am using Play 2.8.2 and try to redirect all HTTP requests to HTTPS automatically, I have added following lines in application.conf file:
play.filters.enabled += play.filters.https.RedirectHttpsFilter

just followed the instruction:
https://www.playframework.com/documentation/2.8.x/RedirectHttpsFilter

I have a certificate and https://www.mywebsite.com works ok.

but the first time I put www.mywebsite.com, it does not automatically redirect to https and it serves from plain http.

However, after I manually input https://www.mywebsite.com, then input www.mywebsite.com in a new tab, it can automatically redirect to https://.

but, after I cleaned the Chrome’s cached data ,“www.mywebsite.com” does not automatically redirect to https any more…

However, after I manually input https://www.mywebsite.com,“www.mywebsite.com” can automatically redirect to https:// again

Why it can not automatically redirect at the first time?
Am I missing something ?