This is a new issue Invalid length parameter passed to the LEFT or SUBSTRING function error message in Microsoft Dynamics GP 2015
Invalid length parameter passed to the LEFT or SUBSTRING function error message in Microsoft Dynamics GP 2015 – Microsoft Dynamics GP Community
Install, Upgrade & AdminMicrosoft & the GP EcosystemGP 2015
Archived post from 2015. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.