2 Things come to mind why they may not show up !
1 - you've NOT installed the Gauges in the right place
maybe ??
2 - those Gauges that came with the download , are too old and for Flight Simulator 1998 up to 2002 maybe
?
I'd suggest you go find the PANEL Folder for that aircraft, OPEN it up and you should see a list of all the gauges and to the Right of the list,,, you should see some Dates they were created , IF they say anything for example, 1998 or 2000 or 2002, they may NOT show up in your Simulator,, their too old.
IF that being the case, then you'll have to go FREEWARE shopping for another aircraft similar to that one and MAYBE, not always swap the panel and gauges from that aircraft into the aircraft you have now, that's a MAYBE tho.
IF none of the Above applies to your situation
Guess what, I can't help ya !
Call 1-800 - 555-555-5555 ask for Clicko'