Blocked a frame with origin

My forms were working till recently and now I am getting the following when trying to submit.

[Error] Blocked a frame with origin “http://www.mydomainname.com” from accessing a frame with origin “https://www.mydomainname.com”. The frame requesting access has a protocol of “http”, the frame being accessed has a protocol of “https”. Protocols must match.

Thank you for any help on this.

https://ww.wp.xz.cn/plugins/custom-contact-forms/