The security cert expired, which it does every 13 months or so. Rogean needs to replace it with a fresh one.
Until he does, hackers could (hypothetically) intercept your Magelo updates, or other wiki edits. Your browser doesn't understand that, thinks your credit card is going to be stolen, and freaks out.
As a workaround some browsers might have ways to disable invalid https certificate warnings, but if they do they will be "secret" (eg.
https://dev.to/moshe/a-secret-way-to...acy-error-4h6i), because browsers
really don't want peoples' credit cards getting stolen.