Neil, if TMC is telling you there is no connection, this is a USB issue, obviously.
First off, you have the correct version of TMC for Windows.
FireWire driver I am running is Version 1.30f9 (I believe it is a Beta from years ago) You run it in Legacy Mode. Easy enough to figure this out via Google if you are not already familiar.
Things to remember: When you install either the FireWire drivers or TMC, make sure the DM is not connected to the computer, not the FireWire or the USB. You connect the DM after you have the drivers and software installed. **Note** Do not unplug or plug in the FireWire Cable while the DM is on, only when it is off. Not following this rule can bake your FireWire card.
To install TMC on Win 10, do it as Administrator and in Windows 7 Compatibility Mode. If you don't know how to do this, Google it, it's important.
Now, back to the USB issue. Check your connection: is it USB 2 or 3? If it is 3, then plug it into a USB 2 port. USB 3 does not always play nice with older gear and can show no connection at times. You can also check your connection via Device Manager where you can disable and re-enable the Tascam DM3200 under Sound, Video and game controllers. This often fixes the connection.
As for Cubase Crashing, as you have described it, I doubt it has anything to do with the DM.
One other thing, make sure you have updated your system, and do a quick reinstall of Cubase to be on the safe side. You do not have to uninstall Cubase to reinstall it, just start up the installer and select reinstall. Sometimes things just go wrong in an initial install and it is a good precaution to take when trouble arises.
Lastly, the Tascam. com site still has drivers and manuals available for download, although not the Beata drivers some of us have.
It would also help if you took the time to post your system specs in your signature to help us better help you. The more pieces to the puzzle we have, the better chance you have for a solution.
Jack