Database connection error after Windows 10 upgrade on server; Windows 10 issues

Press Windows key+X on keyboard to display quick access menu.
Select Control Panel.
Type in 'sharing' in upper right.
Select 'Manage advanced network sharing'.

Enable:
Turn on network discovery
Turn on file and printer sharing

Click expand arrow for All Networks.

Enable:
Turn on sharing so anyone can read/write to Public folders
Turn off password protected sharing

Save changes (button at bottom of page).
Now try your RMS or add-in connection.
You may need to restart PC for changes to take effect.

If RMS or an add-in runs slowly after a Windows 10 upgrade or displays a message related to the Windows Installer, perform the following steps as well.
Control Panel, Uninstall a program, locate and uninstall Microsoft Dynamic RMS.
Install RMS using the download installer (if CD is not available) followed by any hot fixes required to match version of RMS running on other PCs. See Store Operations Manager, Help, About to locate version/build.

Printing issue --

If a PC was upgraded to Windows 10 and a barcode label printer is attached, you will likely need to reinstall the Generic Text-only driver assigned to the appropriate port. Devices & Printers, Add a printer, "The printer I want isn't listed", Add a local printer with manual settings, Next, select correct port, Next, Manufacturer = Generic, Generic/Text Only, Next, name it "Labels", share if required, do not set as default and do not test print. 

Also select Settings, Devices, Printers & scanners, scroll down and turn off "Let Windows manage my default printer".

Startup folder ---

If a PC upgraded to Windows 10 was loading apps from the Startup folder during restarts, those apps may need to be added to the startup folder for Windows 10. First make sure to login to Windows as admin user. To view the Windows 10 startup folder enter "shell:common startup" into the Run command line (Windows-R shortcut). Add any missing app shorts and set compatibility mode to "Run as administrator for all users". If this fails to run a shortcut added upon Restart, use Task Scheduler instead. Type scheduler in Cortana search, Add Basic Task, name it, select 'When computer starts', Start a program, locate shortcut, Finish.

Windows 10 on new PC: When installing RMS on a new PC already running Windows 10, you should first install SQL Server Backward Compatibility (BC) before installing RMS. 
BC 32 bit installer:  www.digitalretailer.com/files/SQLServer2005_BC.msi 
BC 64 bit installer:  www.digitalretailer.com/files/SQLServer2005_BC_x64.msi 
Also make sure Windows Updates are current after installing BC and RMS.