The invoice acknowledgement number is not generating at all when I print invoices. What could be the reason and how can I fix this?

To generate an invoice acknowledgement number in the sales invoice, you need to follow the below steps:
Step 1: To generate an e invoice acknowledgement number in BUSY, ensure that e invoice confirmation is done in GST or VAT.
Step 2: Also, make sure that your QR code print option is enabled in the Sales invoice bill print option, as well as Print E invoice IRN, Ack. No., and Act Date.
Step 3: Also, make sure the Voucher Series Configuration option generates an e invoice after the saving option is enabled.
Step 3: After confirming the above option, make sure the e invoice generated in BUSY is successfully generated by using the automatic option.
Step 7: After generation on E Invoice, you will find the option to print the invoice. Click Yes 
After that, confirm whether the invoice format is standard or designed.
If using standard format, the e invoice acknowledgement number will come automatically because of its default setting, which is already ensured in the above steps.
or
If its design format, you need to change in your designed advance format, you need to follow the below option:
1. To change the setting in the exiting advance format, you need to contact your local partner or dealer of BUSY, because its chargeable setting is BUSY. If the local partner or dealer of BUSY is not able to do this,
2. Then we can be BUSY on a chargeable basis.