I also get the same problem with the API when using https as follows:
"Your connection is not fully secure
This site uses an outdated security configuration, which may expose your information (for example, passwords, messages, or credit cards) when it is sent to this site.
NET::ERR_SSL_OBSOLETE_VERSION"
I can continue to use http(no s) and skip past the warning message:
"The information you’re about to submit is not secure
Because this form is being submitted using a connection that’s not secure, your information will be visible to others.", then use "Send anyway".
It would be good to have the option of sending the Gedcom data in a secure manner.
Great charts though!