The Environment Hash Code is used by the portal to obtain a license, or, in an air gap environment it is used by you to obtain a license.
The hash code is automatically generated by the Cachebuilder service.
If the hash code is missing check that the Cachebuilder service account has DBO access to the ServiceManager database. Also check that it is a member of the SCSM Administrators role. The application pool service account also needs to be a member of the SCSM Administrators role.