Let me add an explanation on how you'll be able to gain access to your client's account, skiprichards.
You'll have to make sure that your client will invite you to their account so you can properly manage their books. Once you receive the email, select Accept Invite and your status will now show as an Active Accountant.
If you're using a different email, they will have to resend the invitation. However, if you're still unable to access your client's account, I suggest reaching out to our support team so they investigate this further. They have the tools to securely pull up your account and double-check why is this happening.