Sounds like a temporary 'server unavailable' issue at the HRMS end of the Internet link as per my very first suggestion in my earlier reply. This can happen when they update their software or it was just genuinely busy and not accepting connections.
Don't forget as you are moving from Windows XP to Windows 10 you will need to ensure that your 'railmaster.ini' file content is Windows 10 friendly.
The following assumes that the following lines are not already at the suggested values.
If you use an eLink change "Reset eLink on start=" from 1 to 0
I also suggest if you are using an eLink that the following lines are set
If you are using an Elite then try these instead:
The above are only suggestions and may need further amendments if controller communication issues subsequently arise.