Semi-buried in the FAQ for the Windows 10 November update, there’s some answers available for those who might be wondering why the upgrade is not showing up yet. I’ve seen a few people ask about this already, so here’s the answers:
If the PC has been upgraded to Windows 10 within the last 31 days, the update will not be available. This is to ensure that you can downgrade in the event the upgrade doesn’t work or causes issues.
If you’ve chosen to Defer Upgrades (Settings > Update & security > Windows Update > Advanced options) the update will not be available. Jump back into this settings area and clear the checkbox.
If you installed it the November update it won’t be offered again. To upgrade again, you'll need to visit Microsoft's Upgrade web site and choose to install it from there. It says it's for Windows 7 and Windows 8.1, but it also works for Windows 10 PCs.
Additionally, there’s another potential reason. It could be that you tried to install it and it failed for one reason or another. I had this issue (yeah, I screwed it up) and you can read about how to solve that HERE. In my case, I canceled the upgrade by shutting the PC off.
Also, there's some clarification needed. The 1511 upgrade through Windows Update is considered a consumer option. Those running Windows 10 Pro and Enterprise editions, connected to a company domain, will need to wait until the upgrade is available to deploy. The ISOs from the Volume Licensing Center aren't supposed to be available until sometime next week.