My answer is not so different from Mar Warne's one. After a couple of reboots, my Personal Keyring started asking for google password, I could not say if because of Evolution, Web Accounts, or a Webapps related thing.
In any case, I tried with my google account password, but the dialog window continued to show up. Then I remembered I created a password for third party apps (2-step verication needed), and even if I disabled 2-step, some of my apps, such as Thunderbird or calendar clients still asks for the second password, don't know why.
So I tried this second one, and Evolution opened, showing my calendar multiple times (each time I created it, I suppose).
Just deleted the copies and all started to work again.