Adobe Player install fail: insufficient permissions

Windows 10 Home
Firefox, v53.0.3 (32-bit)
I am logged in as administrator. Trying to install Adobe Flash latest version. No flash on system now. I don't understand why. I've tried to install several times using different downloads. All have failed- see screenshot above.
Have rebooted computer. Have turned off Security software (Malwarebytes, which is an adjunct). Refuse to turn off Kapersky, which has never caused problems with any download.
This has never happened before. Why is it happening now?
