QBOA sign-up not working

Thanks for posting to the Community, @shene.

Let's set up your Firm manually on the QuickBooks Online Accountant website before accepting the invite.

Here's how:

1. Click the Sign up today for free button.
   
2. Provide the credentials needed to sign up for your QBOA account and hit Continue.
   
   
3. You may required to reenter your user-id and password again for confirmation and then click Continue.
4. Once done, click Create Firm.
   
   
5. You're required to enter your accounting firm name. Please make sure that your firm postcode is 4 digits, and then hit Continue.
   

You can now play around with your QBOA account.

To make sure that you have an alignment with your client in adding you as a user, you can go to Company settings and check your email.

Let me show you how:

1. Go to the Gear icon on the upper right.
2. Select Company Settings.
3. Under Company on the left pane, review your email or click the Pencil icon on the Contact info section to change your email.
4. Then hit Save.

You can now let your client resend the email invitation on its end.

There, you can recheck the email invitation and ready to manage your client's book seamlessly.

You can also check this article on how to manage your firm's team members: Manage users in QuickBooks Online Accountant.

In the meantime, you can utilize this page to find helpful articles on how to manage users in QBO and QBOA: Manage users in QuickBooks.

Please let me know if you need further help by leaving a message to this post. I'll be happy to help. Take care!