@fernandosilva - Make sure you have checked all the below:
- The adaptive card JSON values for your radio button control should be in string format, sample below:
{
"type": "Input.ChoiceSet",
"id": "RadioSelect",
"label": "What color do you want? (expanded)",
"isMultiSelect": false,
"style": "expanded",
"value": "1",
"choices": [
{
"title":"A",
"value":"1"
},
{
"title":"B",
"value":"2"
},
{
"title":"C",
"value":"3"
}
]
}
2. Create your output variable in the Dialog instance per the screenshot below:

3. Set the property in your begin dialog trigger event:

4. You should now be able to see the final out in PVA as shown in the below screenshot:

Hope this helps. I was able to get the value in the variable and display as response from bot per the screenshot above. Make sure it is a "STRING" data type output variable.
Cheers,
Yesh