I am unable to install apps via the Play Store on my desktop.

Google Play Store in Genymotion Desktop usually needs Open GApps, and some apps are blocked by root or CPU architecture mismatches. See Install Applications and I can't install or run an application/game in Genymotion Desktop.

Install Open GApps in the virtual device, reboot it, then open Play Store from the Android apps dashboard. If the app still says “Your device isn’t compatible with this version,” it may be ARM-only, rooted-blocked, or require unsupported features. What exact app are you trying to install, and which Android version is your desktop device using?