1. Check INFO: [PICXO-20]. It will list all of the PICXO instances found by the Tcl.
2. If an instance is listed but is not the top level PICXO, then this answer record is relevant.
3. Check that only the actual instances of the PICXO have a name finishing in "picxo_top"
4. If another instance name in the design finishes in "picxo_top", please change the name of this instance (by using vcxo_top for example).
This will be fixed in the next revision of XAPP589.