Email is based on settings -- pretty straight forward. First check that your MX servers are correct for your mail service.
Then, make sure your incoming mail server, port, username, password and connection security settings are all correct. Send yourself an email and then check. Did you get any error messages or are the emails just missing?
Error messages will tell you exactly where to investigate.
Did you check your junk/spam folders to see if emails are landing there?
If none of this applies and all your settings are correct, you'll have to contact tech support for your email service provider and walk through settings with them to try and determine what the issue may be.
If they are and still no emails are arriving, are you getting any error messages.