From the bit of text that you supplied I see that there are two different transistor types, 2N6520 and 2N6517. You have the model for 2N6520, but I don't see a model for 2N6517 that is referenced by Q1 and Q4. Include the definition of .model 2N6517 and it should work for you.
The models of both transistors are included in the Schematic1.spi file. I did not pasted in the post - just did not want to make it too messy. Here they are, including the the model of the diode. Any more thought? Thank you very much.
.model 2n6520 pnp
.model 2n6517 npn
+ is=2.51189e-14 bf=103.1 nf=1
+ br=1.07 nr=1 ise=2.29087e-13
+ ne=1.5 isc=5.24807e-12 nc=1.5
.model m_1n4001 d
That part looks correct. Either the error comes from another part of the netlist, or the model definitions are out of scope of the Q elements that reference them. I would need to see the entire netlist to debug the problem. If you can share the files, then I suggest that you open a service request on SupportNet.