Http:// vs https://

what type of https are you using? By that I mean, do you have it so that you can use either http or https with http being default?

Our tests in environments where https is set up site wide work without any issues. We have seen some cases where sites with selective https have issues because the URL it is testing against is the http version (because that is default) so when entering via https, it will not match (as http://somesite.com/somelink/ is not the same as https://somesite.com/somelink/)

Try actually adding the https in the request so it is not relative. If it works with one and not the other, try adding both (one relative to the root for the default and one with the https in it for when that is the case).

Let me know if you still have issues after that.
Regards,
Don