I just downloaded the file to check it out. There's a typo in the Aircraft.cfg texture= line for that variation. It must match the texture folder name.

[fltsim.xx]
title=FA-18 Hornet RCN126 VX-10
sim=FA-18
model=
panel=
sound=
texture=  <-- This should read RCN26 VX-10
kb_checklists=boeing_FA18_check
kb_reference=boeing_FA18_ref
atc_id=REDX10
atc_airline=Navy
atc_flight_number=RX10
ui_manufacturer=McDonell Douglas
ui_type=F-18A HORNET I
ui_variation=Royal Canadian Navy 126 test and evaluation squadron VX-10
ui_typerole=Naval Strike Fighter
ui_createdby="Microsoft Corporation"
description=The Hornet entered service with the RCN in 1981, suplementing and eventually replacing the Phantom, continuing the RCN-McD legacy that began with the beloved Banjo.