It all started when I noticed a problem with the sound levels in P3D v5. In an effort to fix that, I deleted the P3D v5 client and re-installed it from my saved download. No change in the sound problem. Next I deleted two of the folders called out in Prepar3D_Download_and_Install_Instructions_v5, then restarted P3D, figuring the files would rebuild. Same sound problem, but now my GTN 650 and 750 doesn't start when I switch on the avionics in any of my aircraft. Now I've got a workaround for the sound issue, but haven't been able to get my RXP GTNs working. 

The Garmin Trainer is working fine. I checked the .log files in C:\Program Files (x86)\Reality XP\GTN Simulation\FltSim\64, and they all look good except for this in rxpGtnSim.dll.log:

21/02/06 17:10:57.229 02360 -    ] # rxpGtnSim64.dll version 2.5.28.0
21/02/06 17:10:57.228 02360 INFO ] 
21/02/06 17:13:04.850 08140 INFO ] GTN 750.1 - TRAINER 6624
21/02/06 17:13:08.142 08140 ERROR] GTN 750.1 process not ready: The specified module could not be found., code: 0000007e
21/02/06 17:13:08.145 08140 ERROR]  check if file is missing or your antivirus: C:\ProgramData\Reality XP\rxpGtnSim32.dll

Sure enough, that file is not in my C:\ProgramData\Reality XP folder. I'm not sure what that means, but I really miss my GTN. I use it in my MJ C-47 and all my A2A aircraft (except for the Cub, P-40, and Spitfire), and really would like to get it going again. Please help.

Thank you
 ATB

You should reinstall with the eCommerce installer from the product page at the RXP website.  Uninstall both the RXP GTN(s) and Garmin trainer.  Download and install from scratch with that eCommerce installer as if you are first purchasing.  You will have to validate your email used when you purchased and your license info, but when you do that you will not be charged again.  You should be able to retrieve your information if needed from the F1 web site.

Do not install in a case like this from an update installer. 

This happened to me when I reinstalled my simulator.

Edited May 12, 20215 yr by RXP

fppilot: Thank you for getting back. I followed your instructions and uninstalled, then reinstalled the Garmin trainer and then the GTN software. That all worked, except that I had to "train" McAfee Total Protection to not mess with the GTN downloads. The install took a while, but went fine. Unfortunately, I got the same exact result - Negative Function. Much checking ensued, and I found that McAfee Total Protection had decided to quarantine rxpGtnSim32.dll. I restored it from quarantine, and it did it again. I re-restored it, and saved a copy somewhere else on my computer, and then added rxpGtnSim32.dll into the exclude from real-time scanning list. I loaded P3D v5, and ... IT WORKS!! 

I'll bet that I probably could have done that restore and exclude thing without all the uninstalling and reinstalling, but I don't care, long as I have my GTNs back in my fleet. 

Call me bad, but I even have a 2D version of the GTN 750 in my A2A B-17. Really wicks off the purists.

Thank you
 ATB

2 hours ago, Paughco said:

IT WORKS!! 

That's what counts!  Happy for you!