This is a weird one - when I lauch 1password 4.2b1 on my nexus 5 I get prompted to install the upgrade. I attempt to do so by clicking the Update button and my phone tells me that installation from unknown sources is not enabled.
BUT... It is enabled in settings and I still get told by the updates that it isn't! (I enabled it after the first time I tried the update)
Is there a download link for the .apk file so I can try a manual update?