I have an Ecobee 3 running an electric furnace. I have a 24v adapter plugged in because the furnace only has 2 wires.

We just had a 48 hour power outage from a windstorm and the thermostat is not turning on now that we're have power again. I have had to reset several of the GFCIs today but this adapter was not plugged into a GFCI. I saved the old thermostat I removed and wired it back up and the furnace works fine, so my thought is either the Ecobee short circuited or the adapter blew a fuse? There's no external screws on the adapter so I'll probably have to test those wires with a multimeter.

Anyone ever experienced this? Recommendations?

Does the furnace turn on with the other thermostat?

There's usually a fuse on your furnace circuit board. Check to make sure that isn't blown.

Yes, running fine with the old thermostat

Sounds like when the power came back on it fried your ecobee. Hope I am wrong.

hopefully just your power supply is blown