deepprobe gives error when probing: --- WARNING (SPECTRE-8281): `p0' is not a node nor an instance name.

I am instaniating an analogLib/deepprobe instance at the top level of my schematic to allow probing inside an extracted netlist.

This instance shows up like this in the netlist:

IPRB2 (xcdr_vco.xvco_biasvosc.xosc.XOSCHI_Xosc_Xbfr1_XBFRP_MN0_GATE n0) iprobe

I am also saving the voltage like this:

save n0

For some reason, I get these warnings in the output file:

WARNING (SPECTRE-8281): `n0' is not a node nor an instance name.
WARNING (SPECTRE-8286): Ignoring invalid item `n0' in save statement.

And the voltage waveform on n0 is not saved during the simulation.

Am I doing something wrong here? Is there a better way to probe a net inside an extraction. My ultimate goal is to run PSS simulation and set the "oscillator node" to an internal node of an extracted netlist. But the PSS dialog box doesn't allow you to type in a hierarchical net name, it must be something present in the schematic.