I am unable to generate the e-invoice and e-way bill together. What could be the reason and how can I resolve this?

To generate the e invoice and e way bill together, you need to follow the below steps:
Step 1: Ensure that e invoice and e way bill configuration is done in GST or VAT from Administrator, then Configuration, then Features or Option.
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, from Administration then Configuration then Invoice Document Printing, then find your Sales Invoice, whether it is Standard or Advance. If it is Standard, select the sales invoice and enable the option, or if it is Advance, design it in advance format.
Step 3: Also, make sure the Voucher Series Configuration option generates an e invoice and e way bill after the saving options are enabled.
Step 3: After confirming the above option, you need to go to the particular sale invoice bill, and in that, you will get the transport window. In the transport window, specify the E way bill within the E invoice option required, yes, and fill in the relevant information for e invoice generation and E way bill generation, then click OK.
Step 4: After saving the invoice, you will get a dialogue box asking, Do you want to generate an e invoice (an e way bill generated within the e invoice)? Click Yes. After that, select Automatic Option, and then you will find the Automatic E Invoice Generation Window. In that window, select relevant option Yes if required, or either skip by No.
Step 5: After that, click on the OK option. You will get the check possible error option. Click on the check possible error option in this window. If you have any invalid transaction details, it will show you in red. You need to correct that invalid data by clicking on the red entry.
Step 6: After checking for possible errors, you need to go to the Generate and Viwe E Invoice option, where you will get a summary of the invoice, check the details, and then click on the Generate E Invoice option. Your e invoice and e way bill will be generated.
Step 7: After generation on the e invoice and E way Bill, you will find the option to print the e invoice and E way Bill. Click Yes 
Step 8: After that, your e invoice and E way bill will be printed successfully, and in the sale invoice bill print format, you will find a QR code and an e invoice ID, Ack. No., and Act Date.
By following the above steps, you will be able to generate your e invoice and e way bill together.