I have a Mach 3 usb motion card, purchased 2017, that runs a 16x 5.5 Router bed. Went traveling for 2 months, and on returning, g code files that worked before and manual commands won't move the machine. The screen will not display the toolpath and there seems to be a new second green led by the limit switch terminals that wasn't lit up before. There is a green led in the middle of the board that lights up when I connect to the computer. The second green LED goes out when I cut power to the limit switches.
Does anyone have any Ideas about what could be wrong? I would be very grateful for some help on this.

What make motion card? What version of Windows? Could the Windows version have updated itself on restart? We need more information to be able to help.

Running Windows 10 Home version 20H2 installed on 8/10/2020 so the version hasn't been updated automatically. The motion card is a Mach 3 USB motion card STB4100 that I bought in 2017. does that give you enough information to work with?

Do you have the documentation for the STB4100 and the Mach3 manual?  The first thing to check I think is that the Mach3 plugin for the card hasn't somehow got lost or corrupted.  When you start Mach3 does it give you either a selection box to select the motion controller, or an error message to say that it can't find the plugin?  You could try saving the latest xml config file (look it up in the Mach3 manual) the reinstalling Mach3 and the motion controller plugin.  I recently had a problem with my UC100 USB connected motion controller that turned out to be that the USB connector had fallen off the card!  Being hidden away this wasn't obvious but caused quite a lot of trouble trying to find the problem...so worth just checking all the connectors too.