https is breaking my header and menu

I’ve installed the plugin, and made the relevant page secure. But the secured page has no header and the menu has gone all screwy. I see in prior threads that this is something that used to happen but was fixed, yet I’m still experiencing it. I installed the plugin from my dashboard today, so it should be current.

Any help would be appreciated!

https://paulwhamilton.com/traffic-ticket-information-form-and-payment/

https://www.ads-software.com/extend/plugins/wordpress-https/