Why is the BUSY not allowing me to enter details while generating the e-invoice? How can I do it ?

To allowing to enter details while generating the e-invoice, You can follow these steps : 
 There is need to do proper E-invoice Configuration in BUSY :
 Step 1: Go to Administration menu then click on Configuration option. 
 Step 2: Now click on Features and options then click on GST/VAT button.
 Step 3: Now Enable the E-Invoice required option and click on configure button.
 Step 4: Mention the From Place and pincode on then e-invoice configuration page.
 Step 5: Then enable or disable the next option according to your need and click on ok button to save it.
 Step 6: Then click on GSP configuration and You will see options of enter Webtel and pinnacle ID'S.
 Step 7: Open E-Invoice Portal and click on registration option and enable e-invoicing then Click on left side e-Waybill portal using your existing credentials.
 Step 8: Go to Registration for GSP and Authenticate yourself with OTP then Add New user.
 Step 9: Choose GSP Name as Webtel Electrosoft Pvt Ltd or pinnacle finserv advisors private limited then Enter the appropriate Username and Password and add the user.
 Step 10: Enter the same username along with prefix and password in the credentials table under GST/VAT GSP configuration in BUSY.
 Step 11: Go to Voucher series Configuration and select voucher type and it's series in which you wants to generate E-Invoice.
 Step 12: On the Right side Click on voucher configuration and Enable Transport window and E-Invoice option on right side.
 Step 13: Now add voucher and it's saving time you will see the window,Do you want to generate E-Invoice and then click on it.
 Step 14: You will see transport window fill it accordingly then select Automatic and Check possible errors and resolve it accordingly.
 Step 15: Press F2 and save this window and generate E-Invoice and print E-Invoice.