After installing and configuring Omnivore for Magento 2, you end up with all your products in a "DEFAULT CATEGORY"

See below

This is due to a bug in Magento 2, whereby when we retrieve the categories for the store, the API does not return any data.


This bug was addressed in latest Magento 2 ver  2.3.4 , so please upgrade to this version to resolve the issue.


It can be found here https://magento.com/tech-resources/download


Additional information:

https://github.com/magento/magento2/issues/25269

https://github.com/magento/magento2/issues/25837

https://devdocs.magento.com/guides/v2.3/release-notes/release-notes-2-3-4-open-source.html