@dianeoforegon
I had the issue where I was unable to select "always allow" on keychain prompts for office 2016. I did not modify the keychain in any way and this is a completely fresh restore of OSX 10.11.1 from recovery (I did initially upgrade the unit to 10.11.1 from 10.11 prior to the recovery)
for me the problem was caused by LogMeIn rescue software that was running on the machine (was using it to make some documentation processes easier). I used the LMI utility to close all connections, then I quit the rescue application all together via the application's menu at the top of the screen. I was then able to select "always allow"
this possibility was brought to my attention by @josemaria_cr earlier in this thread. his comment about some software generating "synthetic clicks" is right on the money and seems to be the root cause for most of the users on this thread.
keep in mind that remote access software like this likes to stick around incase you use things like unattended access. it is likely that: unless you terminate the application and its processes 100% you will continue to have this problem. there is even a good chance this software will start up again and persist through a reboot.
I am not sure if TeamViewer is as clean as LMI when a session is ended. I know LMI has the capability to completely remove itself after a session is finished. regardless I would focus on team viewer, as that is likely still the cause of this problem for you.