The error 429 from BigCommerce platform indicates that it can't handle the number of calls ApiDrop is doing in that particular moment.
Is not a severe issue because you just need to wait and retry the sync as suggested in the BigCommerce documentation
https://developer.bigcommerce.com/api-docs/getting-started/best-practices
If you have many products in sync, it could be necessary to upgrade your plan to let BigCommerce accept more incoming calls.
