HTTPS Monitoring Failing on Version 11.6.0

Our ciphers get more and more restrictive as you increase in version and we weed out insecure ciphers. I would recommend starting here: https://support.f5.com/kb/en-us/solutions/public/16000/500/sol16526

This will explain how to modify the ciphers used by a custom https monitor. If you don't have a customer https monitor you will need to create one. You can see which ciphers are supported here:

https://support.f5.com/kb/en-us/solutions/public/13000/100/sol13163.html

Be aware that if your servers are significantly out of date you may need to upgrade them to get a mutually acceptable cipher.