You went to the Jira Software product pricing page in order to sign up for...

When you go to the Jira Software product pricing page, you can sign up for a new Atlassian site by clicking the Try it free button. You will be asked to enter your email address and choose a site name and URL. However, you must use an email address from a non-public domain, such as your company or organization domain. You cannot use an email address from a public domain, such as Gmail or Yahoo, because they are not allowed for security reasons12

References = Sign up for an Atlassian Cloud site, Atlassian Cloud site and organization domains