SSL tools SSL checker
Check whether the certificate on your site is installed correctly and when it expires — straight from the server, not from a browser.
A browser can show a padlock even when the installation is incomplete (e.g. a chain-of-trust link is missing), because it completes the chain from its own cache. This tool connects directly to the server, exactly like a device without that cache would, and shows exactly what the server sends.
Still no padlock? Check why no padlock, or read the certificate in detail.