I got invitation for accountant but QB doesn not adding me and ask for sign in and when I enter my credentials it does not accept my account , what should i do ?

Hi Zafar, you can provide your firm ID to your client so they can invite you directly from their QuickBooks Online account.

To invite an accountant using the firm ID, you can refer them to this article: Invite Accountant Users.

Once they send the invite, you can accept it by navigating to the Clients section and selecting the Client Invitations tab within your dashboard.

Don't hesitate to reply here if you require further assistance.