It's best practice to check Junk/Spam folders in case the invitation email has been incorrectly flagged by your email provider.
Also, if you have multiple email addresses, it's a good idea to check all of them in case you've used an alternative email address when applying for the job (as that is the email address that would've been used to invite you to the Assessment).
Failing the above, please start a chat (green button in the bottom right corner of this screen) with your full name, the name of the company you're applying for and the job/role you've applied for and we'll be able to manually send you a new link.