Thanks for replying alyssafriesen.
I figured out why that one machine couldn't pass the 'Login not required' problem. It was because the Meraki Agent wasn't installed on the machine. The meraki web ui said it was installed, but the last time the meraki confirmed this with the machine was many many months ago. Since that time, the machine had been wiped and given to a new user.
I stopped receiving these policy violation emails once I installed the Agent on that one machine.
Then I checked all the other machines, to see what the Meraki Agent last-checked dates were for each machine, and there were a few offenders. Very soon after I viewed the apps list for each machine, I started getting policy violation emails again - this time about the screen lock timeout policy. Up to 10 people were violating the policy, myself included, and I was definitely NOT violating the policy.
Other work took over for a few days, and then I realised I'd stopped receiving the policy violation emails. As of this moment, all machines are compliant with the policy.
Why did meraki suddenly complain about 10 people screen timeout? I don't know, but it got over it.
This feature is really quite badly broken. I imagine it will not be too long before it decides to send violation emails again.
Alyssa, I recommend you double-check that the Meraki Agent is installed, and running, on the devices. Check for `ls /var/log/m_agent.log`, and for the m_agent process ( `ps aux | grep m_agent` )