I'm not sure if it your problem is with the L-1011 (32bit), or the L-1011 II (64bit), but either way, it's most probably due to the l112.sys!main/y112.sys!main gauge missing from the panel.cfg....

L-1011 32bit for FSX/SE/P3Dv3

Make sure that the l112.sys!main gauge is listed in the [Window00] section:

[Window00]
background_color=0,0,0
size_mm=1024,768
window_size_ratio=1.00   
position=7
visible=1
ident=MAIN_PANEL
render_3d_window=0
window_size=1.000, 1.000
window_pos=0.000, 0.000
gauge00=l112.sys!main, 0, 0, 1, 1
gauge01=l112.sound!main,1,0,1,1,Captain_Sim\1011\sound.ini

L-1011 II 64bit for P3Dv4

Make sure that the y112.sys!main gauge is listed in the [Window00] section,like this:

[Window00]
background_color=0,0,0
size_mm=1024,768
window_size_ratio=1.00   
position=7
visible=1
ident=MAIN_PANEL
render_3d_window=0
window_size=1.000, 1.000
window_pos=0.000, 0.000
gauge00=../../CS_L-1011-1/panel/y112.sys!main, 0, 0, 1, 1
gauge01=../../../../Captain_Sim/bin/cs.sound.panel!main,   1,   0,   1,   1, Captain_Sim\1011-II\sound.ini

Note. If you add the gauge to an existing [Window00] with other gauges, make sure that the gaugeXX=, is the next gauge consecutively. ;)