Greetings,
Thank you for asking.
As far as there is no output shown to your which kind of error is the NitroPack interface getting, I suspect it’s a 403 or something else from Cloudflare’s Bot Fight Mode feature, if so, or any other security related if you’re using some custom-made Firewall Rules 
Kindly, may I ask you to navigate and double-check the CF dashboard → WAF for any Firewall Events if they show if the NitroPack request is being challenged or blocked a minute or two after you click the button to confirm those changes at NitriPack interface?
Furthermore, I believe the article from below could help you with correct way using the step-by-step instructions how to setup NitroPack with Cloudflare for your domain: