I installed CM 13 on my M8 last night, and contacts won't sync. I installed the OpenGapps package that they recommended, and signed into my Google account. Everything works, but contacts won't sync in either the contacts app that came w/ CM 13 or the official Google contacts app that I downloaded from the Play store. I tried messing with account sync, and people do sync but the contacts don't show up. All of my contacts are still at contacts.google.com. I tried deleting my Google account and resigning from within the contacts app, but that still didn't get them to sync. I'm too lazy to reinstall CM so that's more of a last resort.