I’ve been having some issues with the gmail app not syncing properly on my Nexus 4 phone lately.

Thought it was related to an OS update, but it turns out that it wasn’t.
It’s been happening to a lot of others and apparently google is investigating. In the mean time, this post’s description has solved my syncing problems (thanks Tracy): https://productforums.google.com/d/msg/gmail/KQh9H1ldyPc/cJmBqj4q2tEJ