Could not instantiate ESH connectivity: Connection Guid &1 is invalid

What causes this issue?

The system tries to access the Enterprise Search (ESH) connectivity to
SAP HANA or to TREX/BWA via a "connection GUID". The connection guid is
not found, or invalid, or not properly configured. The ESH connectivity
cannot be used.
The error can arise in the following cases:
Enterprise Search and the ESH connection have not yet been set up on the
system for the local working client
There are duplicate local connectivities, for example after a system
copy or client copy. In this case, the invalid (copied) connectivity has
to be removed, and any legacy entities (for example search connectors)
belonging to the legacy connectivity have to be either deleted or
migrated.
The local connectivity is correctly set up, but there are legacy
entities (e.g. search connectors) still referring to an invalid
connectivity. Also in this case, the legacy entities have to be deleted
or migrated.
If you are using a remote connectivity to a secondary system: that
connectivity may not have been set up correctly
For CDS-based search connectors an initial activation process may not
have succeeded

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

Access to the Enterprise Search services, features and entities is not
possible.

How to fix this error?

The ESH connectivity has to be cleaned up.

Procedure for System Administrators

Depending on the use case you can do the following:
If Enterprise Search has not yet been set up at all on the system:
Run Task List SAP_ESH_INITIAL_SETUP_WRK_CLIENT
If there are duplicate connectivities or if there are legacy search
entities which have to be migrated after a system copy or a client copy:
- Run Task List SAP_ESH_ADJUST_AFTER_COPY (in case of a system copy)
- Run Task List SAP_ESH_ADJUST_AFTER_CLIENT_COPY (in case of a client
copy)
Note that depending on the SAP Basis release of the source system and
depending on the status of the legacy connectors there may be cases
where they cannot be recovered.
If there are legacy entities which have to be removed:
Run e.g. Task List SAP_ESH_CREATE_INDEX_SC with steps "Delete" and
"Create & Index (New) Connectors"
To clean up everything, you can alternatively run Task Lists
SAP_ESH_RESET and then rebuild the connectivity again with
SAP_ESH_INITIAL_SETUP_WRK_CLIENT
To check the consistency of the setup you can run task list
SAP_ESH_CONSISTENCY_CHECK
Alternatively, in on-premise releases it is possible to set up and
configure Enterprise Search manually, e.g. via the customizing tools
available in the IMG. The ESH connectivity for the local system can also
be set up directly with report ESH_ADM_SET_TREX_DESTINATION.
For details refer to the Enterprise Search setup guides and/or SAP
Documentation provided for your release.
For managed cloud releases contact your service partner.

Error message extract from SAP system. Copyright SAP SE.