Update: I changed my Defender "blocking" threshold from low to moderate threat, ran a virus scan, and it installed. Thanks! Will try it out later today.

No Im on 10, latest updates. I'll check my app and browser control.

Alas, comrade: Multiple attempts. Defender refuses to install the tray. Period. No idea why; I presume it's trying to protect the virginity of the precious WMR. I'll keep trying.