From other merchants, I have read that you can no long bulk upload Google Shopping related data.
To resolve the issue, make sure to add a bar code and brand value in Shopify.
If you don’t have this, go to Google Merchant Center > Products > Feeds > click on the feed > feed rules.
Now add a feed rule to set identifier exists to the value no
More info: https://support.google.com/merchants/answer/7450276?hl=en