This can happen if the Accounting subscription was purchased, but not assigned to the user. CORE offers various subscriptions and each user is associated with a subscription, as needed. The CORE account owner can add new subscriptions to CORE. Right after you purchase the subscriptions, CORE checks if the logged account is missing any of the purchased subscriptions. If any of the subscriptions are missing, CORE prompts you to assign subscriptions automatically to your account. If you prefer, you can do so manually from the Manage Users screen. Check CORE Help Center for details.
Please check with your Sales Account Manager to purchase the required subscriptions.