You do not have display authorization for group &

What causes this issue?

To display planning parameters, you must have display authorization for
authorization group &V1&.

System Response

The authorization object for planning parameters is called G_820_GPL
and is made up of the authorization group and the activity, which has
the value 03 for display authorization.

How to fix this error?

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

Error message extract from SAP system. Copyright SAP SE.