Configuring a Citrix ADC / Netscaler monitor for AD FS labels the service as down with the response: “Failure – TCP connection successful, but application timed out”

I recently received a question from someone who had issues setting up a monitor on his Citrix ADC / Netscaler appliance and who had come across my previous blog post:

Configure Citrix ADC to load balance Microsoft Active Directory Federation Services (AD FS) on Windows Server 2019
https://blog.terenceluk.com/2020/05/configure-citrix-adc-to-load-balance.html

The issue he had was that the HTTP monitor he had set up would fail with the LAST RESPONSE from the AD FS server as: Failure – TCP connection successful, but application timed out

I haven’t come across this issue before but after going through the settings with him, we determined that he had forgotten to specify the destination port in the monitor as shown in the screenshot:

I hope this helps anyone who may encounter this issue during their configuration.