Scott T.

@GeorgeM This is a known issue and we have a developer looking into the problem. It's due to invalid date getting into the system, possibly via a 3rd party Evernote client, which is impacting the system that sends out the emails. The invalid data is likely not in your account, though. But the data in one account can cause the email sending system to halt in order to avoid any further problems.

The team made more improvements yesterday and our system metrics look significantly better. So far we have not been able to reproduce the "syncing temporarily paused" issue today. 
We're continuing to make performance improvements, but let me know if this issue persists. We think it's possible you may see this rarely still, but the likelihood should be reduced significantly.

Entering a phone number is required to initially enable 2FA. Once enabled, however, you can choose to use an authenticator app instead of SMS. Having the phone number on file gives you a fallback in case something happens with the authenticator app.

@CalS Yes, we are in the process of migrating all the email sending to a new system. We were just turning it on and had a few issues. It's been disabled for now until we address the problems.

@jonnyb Glad to hear clearing cache worked for you. The web client maintains state in the browser so that if you leave and come back, you don't have to sync down all your notes again. But in rare cases it's possible it can get into a weird state. The team is definitely aware and working to fix these kinds of issues. There's a major improvement coming in the future to how syncing will work and I'm pretty sure it will hopefully address a lot of this.