The error message is caused by the missing of MSIC in the system.
In some cases, certain MSIC codes may not have a corresponding code number listed by LHDN. According to guidance from LHDN officers, users facing this issue should verify their MSIC code through their taxpayer profile in the MyTax system.
To resolve this, navigate to the MSIC configuration settings in your profile, where you can manually add the required code.
Go to e-Invoicing, Configuration, MSIC Code.
Assign the relevant MSIC code to the item and save the setting.
Transmit the invoice again.