Proxy view & is not a CDS view

What causes this issue?

You have entered a proxy view. This means that all select statements for
the current view or the
current table are to be diverted to the proxy view. Only CDS views can
be used as proxy views.

System Response

The current view cannot be checked or activated successfully.

How to fix this error?

Either use no proxy view or only a CDS view. Afterwards, check or
activate the current view again.

Procedure for System Administrators

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.