Unrooted but can't check for OTA's

I was rooted earlier on, and had frozen some apps via titanium backup, by doing this I had disabled OTA updates.

I have restored stock firmware (keeping data) by using a KDZ file, but now when I go to software updates in settings, I just see app updates, there is no way to check for OS updates?

Anyway I can re-enable this? I guess doing a full wipe and flash would re-enable it.

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