** Background information:
I did have ISTA-P (3.54.3) running nicely on Windows 8.1 64-bit with a K+DCAN USB lead (never tried ENET but I think it would have been fine). I was using loader V3.2 for ISTA-P.
I also had Rheingold Standalone 3.47.3 running perfectly with K+DCAN USB and ENET cable.
** Setup on Windows 10 64-bit:
After the Windows 10 update (which failed the first two attempts because it turned out the laptop BIOS needed an update first) most applications were fine.
By simply revisiting the COM port settings for my USB K+DCAN to set back to COM9, minimum buffer sizes and minimum latency Rheingold ran perfectly.
Loader V3.2 and ISTA-P was a bit more tricky. I re-ran the Network Config Tool. I tried Loader V4.3. No joy. However I did eventually figure it out and now ISTA-P runs nicely too, and with the excellent Loader V4.3.
The bit you need to know is that on my laptop and possibly others the USB Loopback network connection was messed up during the Windows 10 upgrade and the Network Config Tool didn’t seem to work properly either.
—> The fix was to go into Network Settings, select the USB Loopback which has been renamed “Ethernet 2” and rename it to “USB” then go into its settings just like you would for an ENET lead and set the IPV4 IP to 169.254.0.8 with a mask of 255.255.0.0
Hope this helps anyone and now everything works perfectly.
Note: thanks for solutions above from cartechnology.co.uk