What does product error mean - "Supplier SKU must not contain special characters e.g (/\!@#$%^&*(),=+<>)"? I don't think we have changed those SKUS, is this a new rule of TranslatorHQ? I have look at some and can see the SKU is both in Shopify and REX with no issues as far as I can see?
This is a new rule which will be imposed by Retail Express in the future.
This is not an issue immediately and can be ignored but, it might / will be in the future but it will be many months in the future. So you can safely ignore these warnings for now.
Please try to avoid these characters in your SKU in the future.