I'm exploring Axelor suite and I can't find any info on how to solve this problem :(

[LewisMojica]

Hello, I'm exploring Axelor to make sure that it fits my needs.
When creating an ventilating an invoice this pops up:

Information
The account of a product could not be determined or is not filled. Please fill the missing account on invoice line Product1
but I have searched for more than an hour without being able to solve this. Also, I can't find any info on how to solve this, is it just that I'm not able to find the information or Axelor has very little documentation?

[ple-axelor]

Hello,
You need to fill the account in the invoice line.