Copilot doesn't add a column to the matrix visual

I have a sales report that I would like to add a column to. I am trying out Copilot, and it cannot add the column in the matrix visual, even with the prompt I give it. If it can generate reports, why can't Copilot add a column when I ask it to?
Example: Need to add a SKU column, which is on the semantic model in this matrix visual, but it says the following:

I attempted to add the SKU field from the Sales & Sold Returns table to your matrix visual, placing it after Product Brand and before Item Name. However, the update did not succeed—SKU is still not appearing in the matrix.

This may be due to a limitation in the current visual configuration or a technical restriction. Please verify that the SKU field is not already present elsewhere in the matrix, and that there are no restrictions on adding it. If you need further troubleshooting or want to try a different approach, let me know how you’d like to proceed.