When trying to add a new dual gauge card to a dashboard using the yaml editor I keep getting a spinning icon

[djdarlo]

When trying to add the below...

type: custom:dual-gauge-card
inner:
entity: sensor.pv_power_now
label: "PV"
unit: "kWh"

to a dashboard using the yaml editor the SAVE button is greyed out and I get a spinning icon. Any ideas?