Can I use Fenzly on several devices?

Not at the same time. A Fenzly account is active on one device at a time: if you sign in on a second phone or a tablet, the first one is signed out. It says so on screen, and you receive an email about it, in case it was not you.

The reason is end-to-end encryption: your keys, places, circles and messages live only on your phone, and the server cannot copy them to another device because it cannot read them. Using several devices in parallel is being looked at, but is not available yet.

To move from one phone to another without losing anything, follow the guide Switching phones: the new phone gets a fresh backup from the old one before taking over.