If the email is not in your inbox, check your spam or junk folders. The email is sent from the ePermit Center with the subject line, "Citizen Self Service New User Account Confirmation."
Business email addresses can have issues with their company email server dumping the message as a spam before it ever gets to you. Ask your email administrator to authorize emails coming from Harford County, epermitcenter@harfordcountymd.gov, or set up an account with a personal email address.