Plain-HTTP resource
Why it matters
Loading a subresource or browser fetch over http:// from an HTTPS page is mixed content, which the browser blocks or flags (Lighthouse: does not use HTTPS).
Fix
Use an https:// URL.
Credit
From Google Chrome
Lighthouse flags resources not served over HTTPS and web.dev explains mixed content.
References
- Does not use HTTPSChrome for Developers
- What is mixed content?web.dev
- Mixed contentMDN Web Docs