What to do when people in your team say “I have no feedback” in a design critique session

I started doing design critiques with my team of developers (I am the only designer within my team) to get feedback from them as early as possible and all along the process. I am really trying to engage them as much as possible by making design critique sessions more interactive. But often the main outcome of the session is “I have no feedback”, not really challenging for me. But the real problem is that issues and opportunities arise later in the process when the design has already been validated by the client and users. Some of those problems could have been seen earlier. Why is this happening? Do you have some advice for me?