Another thought.  If you have access to another Win 10 PC and can install the FireWire card in it, try that and connecting the Saffire Pro 40.  If it still will not connect, there may be a problem with the FireWire interface in the Saffire Pro 40.  The Saffire Pro 40, like many audio devices in that era, uses the DICE II chipset internally.  

Ouch, that card not working is worrisome, since I found the same on on my own and asked Focusrite if it would work (it does have the TI chipset recommended by Focusrite). The response I got was that it wasn't one of the cards they specifically tested, so could not guarantee it, but is also the reason I haven't upgraded to Win10.
 
I am not sure if MixControl/firmware versions are playing into this, but those can have as much affect as drivers. Also there is an ohciTool recommended on Focusrite's help pages that would be worth running. In a couple weeks I will probably be in the same boat, so will see if I can get that FW card to work for me when the time comes and report back (I do not want to lose my 24 DSP either).
 
Quick note, all of the recommended cards on that page above are 1394b, and I need a 1394a port for mine.

mettelus
Ouch, that card not working is worrisome, since I found the same on on my own and asked Focusrite if it would work (it does have the TI chipset recommended by Focusrite). The response I got was that it wasn't one of the cards they specifically tested, so could not guarantee it, but is also the reason I haven't upgraded to Win10.
 
I am not sure if MixControl/firmware versions are playing into this, but those can have as much affect as drivers. Also there is an ohciTool recommended on Focusrite's help pages that would be worth running. In a couple weeks I will probably be in the same boat, so will see if I can get that FW card to work for me when the time comes and report back (I do not want to lose my 24 DSP either).
 
Quick note, all of the recommended cards on that page above are 1394b, and I need a 1394a port for mine.

The Syba card that fireberd linked to in post #2 has the correct TI chip, and has a 1394a port.

abacab
 
The Syba card that fireberd linked to in post #2 has the correct TI chip, and has a 1394a port.

Correct, and is the same one I was referring to that I had found and asked Focusrite about (and will end up getting). The 1394a connections are harder to get, and that is one of only a handful that seem to have it anymore. I am not sure which Saffire version the OP has, and cannot speak anymore beyond what is in this thread until I have the hardware to play with.

57Gregy

fireberd
Have you tried the board yet?
 

Yes. Recognized and working, but it just won't communicate with the Saffire.
I guess I have to accept that it won't work on Win 10.

There are is no doubt , it won't work for Windows 10 

The Saffire Pro 40 IS Win 10 compatible, according to Focusrite.
https://us.focusrite.com/downloads/os?product=saffire%20pro%2040
 

I have the original Saffire, not the Pro 40. It's about 10 years old. It still works great on my XP DAW, which is even older that the Saffire.

Ouch, that may be the problem.  
 
Now, have you tried installing the Drivers in a Compatibility mode?  Try Win 7 first if that is an option.
 

mettelus
Ouch, that card not working is worrisome, since I found the same on on my own and asked Focusrite if it would work (it does have the TI chipset recommended by Focusrite). The response I got was that it wasn't one of the cards they specifically tested, so could not guarantee it, but is also the reason I haven't upgraded to Win10.
 
I am not sure if MixControl/firmware versions are playing into this, but those can have as much affect as drivers. Also there is an ohciTool recommended on Focusrite's help pages that would be worth running. In a couple weeks I will probably be in the same boat, so will see if I can get that FW card to work for me when the time comes and report back (I do not want to lose my 24 DSP either).
 
Quick note, all of the recommended cards on that page above are 1394b, and I need a 1394a port for mine.

Well, if I can't get the Saffire to work on my machine with this brand-new firewire card, I'll probably go with a USB interface.
Maybe we can work something out. 

Greg,
can understand that you take every chance to keep the saffire pro 40,
cause it´s awesome , but at a certain point it´s time to look for a new one.
The good point is that focusrite is offering now  the clarett (usb) interfaces.
Sooner or later it is time to go ahead.
Hope it will take some years til I have to change.
 
regards