Did you get it working? I was getting the same error and then I found this guide. It works fine now.
https://blueiristips.wordpress.com/2019/12/19/set-up-stunnel-on-blue-iris-5-server/
Just ordered 4 IP8M-T2499EW on Amazon to replace my old Swann NHD-818 4MP cameras that are not ONVIF compatible. The code QUCJSYET is valid as long as it's being sold by Amazon. Brought each one down to $89.99. Thanks to the person that posted that code here.