LinkedIn API: Creating UGC Image Post for Organization 500 response - linkedin

Question

I'm attempting to post images to organization linkedin pages. I'm working off of this documentation: https://learn.microsoft.com/en-us/linkedin/marketing/integrations/community-management/shares/ugc-post-api
So far I have the following working:
shareMediaCategory type "ARTICLE" shared to a person
shareMediaCategory type "ARTICLE" shared to an organization
shareMediaCategory type "IMAGE" shared to a person
When I attempt to post with shareMediaCategory type "IMAGE" to an organization, I get the following error response:
{
"message": "Internal Server Error",
"status": 500
}
Here is the url:
https://api.linkedin.com/v2/ugcPosts
The Headers (I have tried with and without all these headers):
Authorization:Bearer REDACTED
Content-Type:application/json
X-Restli-Protocol-Version:2.0.0
x-li-format:json
And the body:
{
"author":"urn:li:organization:2414183",
"lifecycleState":"PUBLISHED",
"specificContent":{
"com.linkedin.ugc.ShareContent":{
"shareCommentary":{
"text":"Hello"
},
"shareMediaCategory":"IMAGE",
"media":[
{
"status": "READY",
"description":{
"text":"Here is the description"
},
"media":"urn:li:digitalmediaAsset:C4E22AQFdCtnVOTxQCQ",
"title":{
"text":"This is the title"
}
}
]
}
},
"visibility":{
"com.linkedin.ugc.MemberNetworkVisibility":"PUBLIC"
}
}
The organization id is a LinkedIn test org ID: https://developer.linkedin.com/docs/guide/v2/organizations/development-testing
I can post articles to that ID, but images 500.
I've tested that the image has been uploaded successfully.