Which version of ArduSub are you using? The DVL integration requires using the “Beta” release (4.1.0) - it won’t work on the “Stable” release (4.0.3).
I searched our docs for “Guided Mode” and the first result is this page, which has a note that says
There’s some further brief commentary on that here. Regardless, modes that require a position estimate understandably can’t be switched into without active position measurements, so you’ll need to fix the DVL connection/integration issue first.