Successful manual integration, but optin prompt doesn't show up

I recently migrate Webpushr to my site https://thinkzone.vn/ (manual integration). Troubleshooter says everything is okay, I did all the setup for optin prompt as instructed, no errors were reported. But no opt-in prompt shows up when I and my friends visit the website (I even tested immediate mode and other modes for the prompt).

Please check and help me.