Help with CalDav sync on IOS 11+

I want use calendar app and synchronizing with iOS. I followed the user manual and used iphone with iOS 10.3.3,it can verify the account and sync successfully , but used iphone with iOS 11.* or 12.* can not verify the account (my server does not support SSL)
I have tried every conceivable setting and connection URL and have followed every guide I can find , but it still dosen’t work

I tried these methods:
1.use and even only the domain name nothing else
2.change port to 80
3.service discovery is working , I tried change the connection URL to :

do you have any idea what i could do ?

The URL which is given in the user documentation worked well for me in the past.

thanks for your answer
the URL in user documentation worked well on IOS 10.3.3 for me, but can not verify the account on IOS 11.* / 12.*

I believe Apple has dropped support for synching CalDAV and CardDAV without SSL with iOS 12 or even with iOS 11.