Work through these in order. Most problems are one of the first three.
The website will not load
1. Is it just you? Check on your phone with wifi off. If it works there, it is your local network or a cached DNS answer, not the site.
2. Is there a certificate warning? A new domain, or one that has just been pointed at us, needs about 15 minutes for its SSL certificate to issue. If it has been longer than an hour, tell us.
3. Is the account suspended? An unpaid invoice past seven days suspends hosting. Your dashboard says so plainly at the top if that is the case. Paying restores it within minutes.
4. Did the DNS change recently? Open Domains in your dashboard and check the A record points where you expect. If you changed it in the last hour, give it time.
Email is not arriving
1. Is the mailbox full? Check Email in your dashboard. A full mailbox rejects new mail and the sender gets a bounce. Clear the Trash or increase the quota.
2. Is it in Junk? Check the spam folder in webmail, not only in your mail app.
3. Did the MX record change? If someone repointed the domain and did not keep the MX record, mail will be going to the wrong place. The presets in your dashboard always preserve MX.
Email will not send
Almost always the SMTP settings. Use port 465 with SSL/TLS, and your full email address as the username. Some cafe and hotel networks block outgoing mail ports entirely, so try on mobile data before assuming it is broken.
The site is slow
Check your storage in the dashboard. An account close to its disk limit slows down. If your visitors are mostly outside South Africa, the CDN add-on will make a noticeable difference.
Still stuck
Ask Hostiy. It can see your account, your DNS and your service status, and it will either fix it or put it in front of a person with all that context attached. You will be told which of the two happened.