Item allocation key or configuration not specified error dynamics 365 finance and operations

I was getting the below error while trying to upload the forecast in Dynamics 365 F&O.I'm using a custom data entity for uploading it into the system.

Item allocation key or configuration not specified.

Reason: product variants are missing.

Solution:  There are two ways to fix the issue

1. upload the forecast with product variants color, size, style and configuration.

2. Default the variants on the product master. So, that when you upload the forecast it automatically takes the variants from the setup.