Why interface not found?

Question

Yii

Downloaded this extension https://packagist.org/packages/pistol88/yii2-liqpay.
Installed - everything is ok. Implemented the interface (phpstorm helped and highlighted). But despite the fact that the IDE is doing well - the error Interface 'pistol88\order\interfaces\Order' not found.
Why does the editor find this class and switch to it, but in fact the error

Answer 1

Changed interface namespace
from pistol88\order\interfaces to namespace pistol88\liqpay\interfaces ;