I recently upgraded my desktop and my Asus Vivo Note 8 tablet to Windows 10 Anniversary update. After the update I can no longer attach indicators or do a debugging session in the metaeditor using MT4 builds 971 & 988. Using build 950, I was able to attach and debug in my tablet.
The weird thing is that on updated desktop, everything works as expected.
In my experience, OS upgrades don't always run smoothly and applications misbehave, expecting certain older conditions to be in place or don't recognize the new environment correctly at all. I prefer installing the OS from scratch (clean install).
However, in this case, try to uninstall MT4, reboot, and then reinstall it again, so that it will take into account the new environment.
I currently have 3 devices with Windows 10 all running with any problems - a HP ENVY-27 Recline desktop (touch screen), a Dell Inspiron-Duo notebook (touch screen) and also a white-label 10" Windows 32-bit Tablet.