ElasticSearch Watcher simulate fires the action, otherwise it's stuck - elasticsearch

Question

I have a slack action configured. All aspects appear to be set up correctly. If I go to my watch's simulate section and choose execute (not ignoring the conditions) it executes fine and the message appears correctly templated in slack. If I save the config and let the watcher run it doesn't send. If I use the email action, it sends the email. If I use both, it sends neither.
{
"trigger": {
"schedule": {
"interval": "1m"
}
},
"input": {
"search": {
"request": {
"search_type": "query_then_fetch",
"indices": [
"elastic"
],
"rest_total_hits_as_int": true,
"body": {
"query": {
"bool": {
"must": {
"match": {
"level": "ERROR"
}
},
"filter": {
"range": {
"#timestamp": {
"gte": "now-1500m"
}
}
}
}
}
}
}
}
},
"condition": {
"compare": {
"ctx.payload.hits.total": {
"gte": 1
}
}
},
"actions": {
"notify-slack": {
"throttle_period_in_millis": 5000,
"slack": {
"account": "monitoring",
"proxy": {
"host": "proxy.example.com"
"port": 3128
},
"message": {
"from": "watcher",
"to": [
"#elk-cluster-alerts"
],
"text": "Elk Error Alerts",
"icon": ":chuck:",
"attachments": [
{
"color": "danger",
"title": "Elk Error Alerts",
"text": "Roundhouse kick!"
}
]
}
}
}
}
}
UPDATE:
Not a fix, but the configuration works when I use a webhook instead of the slack config