Work through these in order. The order matters, because each step rules out a whole class of cause and the early ones are far more common than the late ones.
1. IS IT ACTUALLY DOWN, OR JUST DOWN FOR YOU
Try the site on a phone using mobile data rather than your own Wi-Fi. If it loads there, the site is fine and something local to you is not — usually DNS caching or a browser extension.
2. WHAT DOES THE ERROR SAY
The message tells you which layer failed, and they mean genuinely different things:
A browser message about not finding the server is DNS. The site is not being reached at all.
A 500 error means the server was reached and your application failed. That is code or configuration, not hosting.
A 403 is permissions. A 404 is a missing file or a broken rewrite rule.
A database connection error means exactly that, and usually follows a changed database password.
3. WHAT CHANGED
Almost every outage follows a change. A plugin update, a theme change, an edited configuration file, an expired card. Undo the most recent change before trying anything clever.
4. CHECK THE OBVIOUS ACCOUNT THINGS
Is there an unpaid invoice? A service overdue past its grace window is suspended, and a suspended site stops serving. Check Invoices in your account area.
Is the domain still registered? An expired domain takes the site down as surely as an outage. Check Domains.
Is the account over its disk quota? A full account cannot write sessions, logs or uploads, and many applications fail in confusing ways when they cannot write.
5. LOOK AT THE ERROR LOG
cPanel has an Errors view showing the most recent server errors for your account. For a 500 error this usually names the file and line, which turns guesswork into a fix.
6. OPEN A TICKET
Tell us the exact error text, what you changed and when, and whether it fails from another network. Those three things skip most of the back-and-forth.
If the site is compromised rather than broken, say so — restoring a backup without closing the hole means being back here in a few days.
Troubleshooting