How do I check if my BUSY is ready for e-invoicing generation? What settings should I verify?

You can follow the below prerequisites and required configurations before start generation of einvoices :
Step 1: To generate an e-invoice bill in BUSY ensure that e-invoice Configuration is done under GST and VAT and you have specified the correct GSP Credentials
Step 2: Mkae sure you have enabled the Generate E-invoice option for the series.
Step 3: Transportation details should be enabled 
Step 4: UQC must be spefied in the Unit Master.
Step 4: At the time of saving the invoice you will get a dialogue box asking Do you want to generate an e-invoice Click Yes After that select Automatic Option and then you will find the Automatic E-Invoice INR 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 View 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 invoice will be generated
Step 7: After generation on the e-invoice you will find the option to print the e-invoice Click Yes 
Step 8: After that your e-invoice 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