Hey, ​@theleadershipacademybysg 

When you have the trigger “user comments on your post or reel” your first message has to be “send as a comment” and you’ve set it right, but if you want to do some follow-ups for those who didn’t click the button, you’ll need to add another message block before the button with a link.

For example:
Your first message has to have text and a button (without a link). These message should say something like this “Hey, press the button to complete your registration!”.

In the second message block, you can send the text message + a button with a link. 

This is necessary because the way you did, it won’t open the 24-hour window. That’s why your follow-message didn’t work.

Learn more about the 24-hour window here: https://help.manychat.com/hc/en-us/articles/14281199732892-How-to-send-messages-outside-the-24-hour-and-7-day-windows-in-Messenger-and-Instagram and here: https://help.manychat.com/hc/en-us/articles/14281316989724-Instagram-Post-and-Reel-Comments-Trigger

Let me know if this helps