The message usually arrives on a Sunday morning: the website is gone. Before you assume the worst, there are four ordinary explanations, and between them they cover most cases.
1. Is it only you?
Try the site on a phone using mobile data rather than the church wifi. If it loads there, the site is fine and something local is at fault. This happens more often than you would think.
2. Did an invoice go unpaid?
Domains and hosting renew once a year, usually by email, usually to whoever set it up. If that person has moved on, the reminder is going somewhere nobody reads. A site that vanishes cleanly, with no error, is very often an unpaid renewal.
3. Did somebody change something yesterday?
Ask around before you look anywhere else. A volunteer updating a plugin or editing a page on Saturday evening is a far more likely cause than anything sinister.
4. Is the security certificate out of date?
If visitors see a warning about the connection not being private, the site is still there. The certificate that proves it is genuine has simply expired, and it can usually be renewed the same day.
If none of those explain it, that is the point to ask for help rather than start changing settings.