wpi templates not working on multisite

On the Main tab I’ve ticked the:
Use custom templates. If checked, WP-Invoice will use templates in the ‘wpi’ folder in your active theme’s folder.

And I see the green box saying:
A “wpi” folder has been found, any files with the proper file names will be used instead of the default template files.

But templates are not being used. Works perfectly on a non-multisite installation. Suggestions?

https://www.ads-software.com/plugins/wp-invoice/