
When WordPress says the server cannot process the image, the upload almost always worked. What failed is the resizing that follows, which unpacks every pixel of the photo into memory before making up to seven smaller copies. We measured that at about a quarter of a gigabyte for a 48 megapixel phone photo. Since WordPress 7.1 the block editor can do the resizing in your browser instead, while the Media Library still does it on the server, so the same photo can fail in one and work in the other. The fix depends on which limit stopped the resize, and your error log usually says which.
Site Health tests twenty PHP modules and marks only two of them required, so a heading saying recommended modules are missing is almost always a quality ceiling rather than a fault. Read the module names under it, not the heading. Four of those modules are fallbacks for other modules, and a missing fallback is the one case that turns the warning into a red critical — which is why the same screen can go from yellow to red without anything new breaking.

A failed loopback request means WordPress could not reach its own wp-cron.php with a ten-second POST. The code printed under the label is the diagnosis: a cURL error means nothing answered (DNS, firewall, network), a status code means your own server refused (Cloudflare, ModSecurity, a deny rule, or the entry-process ceiling).
