I am receiving the same error when I try to run/install the Zoom App Custom Layout Sample. I tried on Incognito and implemented app.set('trust proxy', true) in the app.js as suggested by Ben - however, this also did not solve the issue for me. Do you have any other ideas what I could try? I would be grateful for any hint.
I found the only way to avoid this if you are using ngrok is to navigate to the https://xxx.ngrok-free.app URL rather than http://localhost:3000. Then click the “click here” to install the app.