When attempting to log into eduroam for the first time on a Mac running macOS 15.x (Sequoia), you may find it impossible to enter your Name & Password when prompted to add the required Certificate. The authentication dialog displays as expected but disappears by itself as if you'd pressed OK or Cancel.
To add eduroam successfully don't use the drop down Wi-Fi menu at the to of the screen but instead navigate to:
Apple menu > System Settings > Wi-Fi and hover over the "eduroam" line to reveal its "Connect" button. Clicking that should allow you enter your account name and password when prompted for the required certificate.
You can also download the certificate file.
And double click to add to your Login keychain: