After installing macOS Sierra the accessibility selection to turn off the built-in trackpad when a mouse is present no longer works. The trackpad remains on.
MacBook Pro with Retina display, macOS Sierra (10.12), Time Capsule 2TB V7.6.7
same here and seems we have to wait until apple update software.
I already sent email to apple a few days ago, and no reply.
I sent Apple a note as well, but I think I found a work around until they fix it permanently. After a reboot it seems to forget the setting but if you go into ACCESSIBILITY and toggle the selection it seems to persist even after waking up from sleep mode. Try it and let us know if that works for you.
I have to go in and uncheck it, then recheck it after each reboot.
For those of you that find this post looking for answer,
Go to System Preferences then Accessibility then scroll down to Mouse and Trackpad then uncheck and re-check Ignore built-in trackpad when mouse or wireless trackpad is present.
I have to use a mouse because my built-in trackpad jumps around and selects things on its own.
Accessibility feature to turn off Trackpad is broken
