Hi Ahmed,

The message "You can't register a payment because there is nothing left to pay on the selected journal items." typically occurs when there are no journal items in a state where they can be paid. This can happen for various reasons, such as:

1. All journal items have already been paid: Check if the journal items you are trying to pay have already been fully paid. If so, you won't be able to register another payment for them.
2. Journal items are not in a state to be paid: Ensure that the journal items you're trying to pay are in a state where they can be paid. For example, if they are in a draft state or already reconciled, you might not be able to register a payment for them.
3. The payment account is incorrect: Make sure that the account you're trying to pay from has sufficient balance and is configured correctly for payments.
4. Payment journal configuration: Check the configuration of the payment journal to ensure that it's set up correctly, including the accounts and payment methods.
5. Permissions: Ensure that the user trying to register the payment has the necessary permissions to perform the action.
6. Filters: Check if there are any filters applied that might exclude the journal items you're trying to pay.
7. Customization or modules: If you have any customization or additional modules installed, they might be affecting the payment process. Check their configurations and code for any issues.

Hope this helps.