Nexus 7 - 2013 - missed 5.0 rollout?
You can direct download the latest factory image here for your device. As far as I know, you need to note several things before force push the update:


Power off your device.
Enter to recovery mode (Power + Volume up and down buttons simultaneously for a few seconds).
Locate the zipped file and extract it to update the version. (May take a while)
Reboot


A bit of warning: Doing this will erase your all of your data and apps. Be sure to backup your data before doing this.

I hope this helps you.