Have you looked for error messages in the Windows Error Log. Have you tried running the compatibility troubleshooter the you can get to when you right click the program icon and select Properties and then click on the Compatibility tab. There also options on this tab to select the version of Windows to emulate for the program.

I ran the compatibility troubleshooter. Still get the issue when trying to open in the previous version of windows. As for the Windows error log...I opened the events viewer but I don't know where any errors for the application would be.

After going through the events viewer I found the following. No idea what it means.
-883431207
5
CLR20r3
Not available
0
simplyaccounting.exe
19.0.0.5
50c71b46
Sage_SA.InteropToManaged
0.0.0.0
50c71328
89
2
System.IO.FileNotFoundException

C:\Users\Nancy\AppData\Local\Temp\WER6173.tmp.WERInternalMetadata.xml
C:\ProgramData\Microsoft\Windows\WER\ReportArchive\AppCrash_simplyaccounting_e7eee2f7b4cc45b9a33a9f3ad7eb569e1956ac5_00000000_145f7dc5

0
c1a18f4b-485c-11e6-bf36-74e54395191b
0
fa84ac564356c42cf1772ae2eab2f5cd

Is this a fresh install of 2012 on Windows 10 or was the OS upgraded to Windows 10 after the software was installed?
Have you tried to reinstall the copy of Sage 2012 or do a repair of the installation

The software was already installed. I tried my laptop as well as it was also upgraded to windows 10 and I am having the same issue there. So it's obviously related to the windows 10 upgrade. I've not done a reinstall (gotta dig deep to find the original file plus all the releases as it was a downloaded version of the software).

ps. how do I try a repair of the installation? Should I try this first before doing a total reinstall?

You can try to do a repair as follows, Control Panel, Programs & Features, locate the Sage 50 installation item, and see if there is an option to "Change", after a number of prompts you should see an option to "Update/Reinstall Program". Make sure that you do not uninstall the program, read all prompts carefully! As a precaution I would check to see if you can locate the installation files and the updates before you do this, just in case something goes wrong! Hopefully you also have the serial number and the key codes etc. to do the reinstall

If you can not find the original files, I might have them on an archive disk somewhere, but it could take some digging which I would prefer not to have to do!

I followed your prompts to the programs and features. However, for both my 2011 & 2012 Sage versions it does not give me a change option, just uninstall. Funny that the 2010 version has a change option. Both the 2011 & 2012 are premium versions while the 2010 is pro. So I'm going to go that route and reinstall to see if that works. I found my downloaded file for the last update to version E and the key code from the original installation.

well...that didn't work. I uninstalled and restarted the laptop. When I started the install it got to the point of extracting files then stops and an error pops up '1628 failed to complete installation'. I had turned off the firewall already...just in case.

I just ran the installer (SA_2012ACP2.exe) on my Windows 10 system and it extracted the files with no problems (My Win 10 system is not an upgrade, it was a clean install).

I suspect that there may be some sort of issue with you Windows 10 installation.  

The only thing that I can suggest is that you use a tool like "7-zip" to extract the installer files and see if the installer will run http://www.7-zip.org/download.html

You should extract the files to "C:\Sage\Sage Simply Accounting 2012 Installer Files – CDN"; in fact you may want to check this location to see if the installer files are already there; as this is the default location for them to be extracted to!

I don't want to test the install on my production Windows 10 system; and my Windows 10 test system is currently in use on another project at the moment!

I downloaded 7-zip....but how do I use it to extract the installer files?

Locate the file "SA_2012ACP2.exe", right click the mouse and select "7-Zip" from the context menu, then "Extract files...". Then put in the path "C:\Sage\Sage Simply Accounting 2012 Installer Files – CDN" (without the quote marks). When the files are extracted locate the launch.exe in the folder and run the installation.

success! Although the 7-zip extracted files did not include the launch.exe file in the folder. However, the original installer files were still in the Sage folder so after uninstalling 2012 I selected the launch.exe file and it reinstalled 2012 and then I ran the update to release E and I am now able to open my 2012 version. Thanks for your help Bruce!