If the SameSide class in /Inbound and /Outbound is accidently deleted, it may need to be re-added manually.
In order to create the proper matching rules, you must create the classes in the CLI.
Use these commands:
class new /Inbound SameSide nodefault inside same-side outside host:any
class set /Inbound/SameSide exception
policy apply ignore /Inbound/SameSide
class copy /Inbound/SameSide /Outbound