PHP Fatal Error: Cannot instantiate interface

Error message

PHP Fatal error: Uncaught Error: Cannot instantiate interface Plumrocket\…\Api\…Interface

Issue Description

This error means that Magento has outdated information about Dependency injection. In most cases, it is due to the cache.

Most likely, you are experiencing this fatal error after running the following command: 

bin/magento setup:upgrade

Solution

You need to clear the cache before running bin/magento setup:upgrade. Please use the following command to clear the cache:

bin/magento cache:flush