For this scenario to happen, the following must be set:

1. Create a Buy together promotion with a price range restriction, like minimum price value.
2. Create a gift promotion.
3. The gift in the second promotion must be one of the Buy Together products on the first promotion.

When this is set, when the client is at the checkout trying to add the gift promotion, it receives an error:

message="Ocorreu um erro de comunicação com o Rates and Benefits"

This happens because now the system is trying to recognize the price range restriction when it shouldn't.

Recreate the steps mentioned above. PS: related scenarios - https://help.vtex.com/known-issues/regular-promotion-using-gift-conflicts-with-value-filters-on-the-cart--oUDvaZPL0fjbN3v18QQIM

Remove the price range restriction on the Buy Together promotion.