Resolved.
I uninstalled v3.1.3 re-downloaded and reinstalled it and it is working now. I must be sure to remember to 'Run as Administrator' as the instructions say or it will not connect, . Edit  (I changed the properties so it will always run as Administrator)

Thanks Tim.
Need some help on checking/updating DotNet. Not familiar with that.
I will check permissions and make sure I run the app under Administration to be sure.. However, both versions access through the same X-Plane link, and v3.1.3 worked the first time tried, just never after.

I have both Plan-G v 3.0.7.71  and v3.1.3  installed and use Windows 10, (although my problem also occurred in Windows 8)

The older version of Plan-G connects to X-Plane without difficulty.  I have the latest version of XPUIC 64 bit installed.
After I installed Plan-G v3.1.3 and used all the same settings as with v 3.0.7.71 Plan-G connected to X-Plan but only once. (the first time I tried using it.) After that v3.1.3 no longer connects to X-Plane although I made no settings changes and they are exactly the same as v3.0.7.71.  Only one installation of X-Plane 10 so the same location etc is referenced in the settings. All the x-plane data files are there and everything else is the same for both versions only v3.1.3 will not connect and v3.0.7.71 does
What am I doing wrong?
Thanks in advance.

I have installed the Beta version v3.1.3.113  and that just completed building the X-Plane 10.42 database with Windows 10.
Thank you for that Beta!

When attempting to Build Navigational Database for X-Plane 10 Plan-G (v3.1.2.101) completes the apt.dat scan then freezes in the (writing 40,798 runways) phase and has to be shut down. I have been sure to allow enough time for it to do this, including overnight, but the progress bar never moves past about 10%. (or the progress still shows 100%[all green] from the previous phase. I can still move around the little window, or click the 'settings' button, but the spinning wheel cursor is always spinning and the "cancel" and OK buttons are greyed out and cannot be clicked. This also happens for an earlier version of Plan-G (3.0)  When I start up Plan-G after that, now it does not have all of the data (such as ILS is no longer displayed regardless of the setting, and there is a message at the top that I must generate the database.
I am using  windows 10-64, and X-Plane 10.42 and a Nividia GTX 760 2GB. I am also using the latest version of XPUIPC (64 bit)

That worked. Thank you very much.  Its working in XP 9 & XP 10 (except XP 10.20 64 bit).
Great!

Apparently not. I just installed XP 9 and updated it. I thought XPUIPC was part of X-Plane.
Just did a search and found XPUIPC for X-Plane version 1.9.0 so I am downloading it now and will install. I don't remember ever doing that for XP10
Thank you

Tracking my aircraft worked fine in XP-10, but when trying Plan-G in XP-9 I do not get tracking.
I changed the 'location' path to the XP-9 directory and I rebuilt the Navigation database to the proper XP-9 directory, but when I 'Connect' the aircraft is not on the map and it does not track. How do I get it to work in XP-9 when it worked in XP-10. All other settings (including IP address) are the same.

I have two installations of X-Plane in different directories. One is for the current stable released version (XP-10.11) and the other is for the current beta version(64bit) XP-20b10 and I am trying to get Plan-G to work for both. Both directories are shared. The installation of Plan-G is in my root directory C:\Plan-G.  My database for X-Plane used the directory for the 10.11 version of x-plane, but the data should be the same. I did not try to import data from both directories since I thought they would be duplicated. I call the directory for XP10.11 directory 10A and the directory for XP 10.20b10  directory 10.
Plan-G works fine in XP-10.11 (the 10A directory). Does not work in the 10.20b10 installation of X-Plane (directory 10)
In Plan-G, depending on which XP version I am runing I change the options 'Location' to the correct directory (10 or 10A). I can 'Connect' in both dirrectories (Plan-G says I am connected) but when running XP-20b10 the connection with Plan-G does not work, The little aircraft in the map never shows. Does Plan-G not work with XP10.20b10 or do I have to reinstall a second version of Plan-G somewhere and import all the data from XP10.20b10 as well? How can I get it to work with both versions of X-Plane?
Thanks

Just to be sure the issue is current, a reboot does not work for me.

I should add that my OS is Windows 7, I am using the latest release of  Plan-G 3.02.51 with X-Plane 10.10 (32 bit version).

I am new to this so my question may be a simple one but I could not find answer in FAQ on the forum. I am unable to clear the flight trail my aircraft leaves when following my flight plan. The 'Trail Analysis' button in 'View' has no affect when I click on the 'X" and it is always blank. I set my options not to log the trail but that has no effect. I deleted the trails in the 'Trail' directory but that has no effect. The only way I am able to get rid or clear the trai is basically starting over by shutting the application down and restarting and loading the flight plan from scratch disconnected from my FS. Is their a simple way to just clear the flight trail without having to restart and reload everything/ (the Trail Analysis button does not work.) Appreciate your help and apologize if I missed something.