Alexa home skill v3 ToggleController skill fails to find devices - alexa

Question

I'm trying to use the Alexa Smart Home Skill ToggleController v3 interface to build a skill that will open and close my gate. I read the docs, and successfully implemented the sample light bulb tutorial from end to end. https://developer.amazon.com/en-US/docs/alexa/smarthome/smart-home-skill-tutorial.html
Everything worked fine. Then I created a new skill and tried to implement the ToggleController interface, mapping ON and OFF to Open and Close using semantics.
Account linking works fine
Lambda gets called with discover directive when I enable the skill on
my Alexa app
There are no errors in CloudWatch
Alexa Simulator calls the right directives and receives responses with no errors
Schema validates successfully
When I click discover devices, I get "No new devices found".
I checked all devices in the Alexa app and my device is not there.
Below is the discovery response message that my lambda returns - (from CloudWatch).
Does anyone know what I'm doing wrong?
{
"event": {
"header": {
"namespace": "Alexa.Discovery",
"name": "Discover.Response",
"messageId": "fedfbae4-0ec8-4b4e-81d1-c998bc0ee860",
"payloadVersion": "3"
},
"payload": {
"endpoints": [
{
"endpointId": "pleasant-view-gate",
"manufacturerName": "Ancient Geeks",
"description": "Smart Gate at Pleasant View Cottage",
"friendlyName": "Pleasant Gate",
"displayCategories": [
"OTHER"
],
"capabilities": [
{
"type": "AlexaInterface",
"interface": "Alexa.ToggleController",
"instance": "PleasantView.Gate",
"version": "3",
"properties": {
"supported": [
{
"name": "toggleState"
}
],
"proactivelyReported": false,
"retrievable": true
},
"capabilityResources": {
"friendlyNames": [
{
"#type": "text",
"value": {
"text": "Gate",
"locale": "en-US"
}
}
]
},
"semantics": {
"actionMappings": [
{
"#type": "ActionsToDirective",
"actions": [
"Alexa.Actions.Close"
],
"directive": {
"name": "TurnOff",
"payload": {}
}
},
{
"#type": "ActionsToDirective",
"actions": [
"Alexa.Actions.Open"
],
"directive": {
"name": "TurnOn",
"payload": {}
}
}
],
"stateMappings": [
{
"#type": "StatesToValue",
"states": [
"Alexa.States.Closed"
],
"value": "OFF"
},
{
"#type": "StatesToValue",
"states": [
"Alexa.States.Open"
],
"value": "ON"
}
]
}
},
{
"type": "AlexaInterface",
"interface": "Alexa",
"version": "3"
},
{
"type": "AlexaInterface",
"interface": "Alexa.EndpointHealth",
"version": "3",
"properties": {
"supported": [
{
"name": "connectivity"
}
],
"proactivelyReported": false,
"retrievable": true
}
}
]
}
]
}
}
}