If you are unable to generate e invoice then there can be several reasons for this.
1. Ensure in party master all details like address, state, gstin, pincode and other details is filled correctly.
2. Also make sure that in item master tax category , hsn code and unit mentioned correctly.
3. Ensure that you have filled all the required details like item price, tax, party details and other details is mentioned correct in voucher.
4. Check your internet connection to ensure it is stable.
5. Make sure you have the necessary permissions and access rights to generate e-invoices.
6. Update your BUSY software to the latest version.