Web service not reachable in Ubuntu

I created a web service, from the dashboard it tells the service is running normally. The URL for this service(assume example.koyeb.app) can be opened from macOS. While on Ubuntu, the browser reports:

Firefox doesn’t trust example.loyeb.app because its certificate issuer is know, …

I’ve tried to reach the URL using curl, the result is the same.

Hi @chengevo,

What Firefox version are you using? For me Firefox and Chrome work ok.