User require to enter correct HSN code and reprocess the invoices for E-Way Bill or E invoice generation.
Also find Steps to check HSN/SAC Code of your product and Services:
Step 1: Open e-way bill portal Step
Step 2: Go to 'Search'
Step 3: Select 'Product & Services'
Step 4: Enter HSN code or Name of product & Captcha
Step 5: Clicks 'Go'
Please
go through the following link