Quick answer: Fix SSL errors with a valid Let's Encrypt certificate, correct Cloudflare SSL mode (Full strict) and no mixed content.
If you landed here: Browser warns "Your connection is not private", Cloudflare shows 525/526 or padlock missing.
Error → fix
| Error | Cause | Fix |
|---|---|---|
| NET::ERR_CERT_DATE_INVALID | Certificate expired | Renew Let's Encrypt in panel |
| Cloudflare 525 | Origin without HTTPS | SSL on server + CF Full |
| Mixed content | http:// resources | Change URLs to https:// |
Setup: Set up SSL · Cloudflare DNS
Frequently asked questions (FAQ)
NET::ERR_CERT_DATE_INVALID – what to do?
Certificate expired. Re-issue Let's Encrypt in panel or check auto-renewal. Clear browser cache.
Cloudflare SSL error 525/526?
525 = origin has no SSL → Cloudflare Full (strict) + Let's Encrypt on server. 526 = invalid origin certificate.
No padlock despite HTTPS?
Mixed content – HTTP resources on HTTPS page. Browser console (F12) → fix mixed content warnings.