Not able to approve invoice from accounting list page

When you trying to approve the invoice number from the account line list page and having issues, check for the following - 

Check if that invoice number is already approved or not ? If the invoice number you are trying to approve is already approved, then in that case when clicking on the 'Approve/Reject' button, will not list that account line.

You can search for the vendor invoice number by following below steps :

Finance >> Find Vendor Invoice