Doesnt receive message from Lemmy

[Nutomic]

For this step (and the one before), I sent private messages from enterprise.lemmy.ml to the indicated user, but nothing happens. It just keeps displaying the same message until I press skip.

Here is the message sent by Lemmy:

{
lemmy_1     |       "@context": [
lemmy_1     |         "https://www.w3.org/ns/activitystreams",
lemmy_1     |         {
lemmy_1     |           "sensitive": "as:sensitive",
lemmy_1     |           "stickied": "as:stickied",
lemmy_1     |           "comments_enabled": {
lemmy_1     |             "kind": "sc:Boolean",
lemmy_1     |             "id": "pt:commentsEnabled"
lemmy_1     |           },
lemmy_1     |           "category": "sc:category",
lemmy_1     |           "sc": "http://schema.org#"
lemmy_1     |         }
lemmy_1     |       ],
lemmy_1     |       "id": "https://enterprise.lemmy.ml/activities/create/3c91610b-719c-4e74-bd4e-d3748a398dae",
lemmy_1     |       "type": "Create",
lemmy_1     |       "object": {
lemmy_1     |         "@context": [
lemmy_1     |           "https://www.w3.org/ns/activitystreams",
lemmy_1     |           {
lemmy_1     |             "category": "sc:category",
lemmy_1     |             "comments_enabled": {
lemmy_1     |               "kind": "sc:Boolean",
lemmy_1     |               "id": "pt:commentsEnabled"
lemmy_1     |             },
lemmy_1     |             "stickied": "as:stickied",
lemmy_1     |             "sc": "http://schema.org#",
lemmy_1     |             "sensitive": "as:sensitive"
lemmy_1     |           }
lemmy_1     |         ],
lemmy_1     |         "id": "https://enterprise.lemmy.ml/private_message/11",
lemmy_1     |         "type": "Note",
lemmy_1     |         "mediaType": "text/markdown",
lemmy_1     |         "source": {
lemmy_1     |           "mediaType": "text/markdown",
lemmy_1     |           "content": "asdasd"
lemmy_1     |         },
lemmy_1     |         "content": "asdasd",
lemmy_1     |         "to": "https://test.activitypub.dev/tests/evaluate/4143414496938641581/alex",
lemmy_1     |         "attributedTo": "https://enterprise.lemmy.ml/u/nutomic",
lemmy_1     |         "published": "2020-12-16T19:41:58.601502+00:00"
lemmy_1     |       },
lemmy_1     |       "to": "https://test.activitypub.dev/tests/evaluate/4143414496938641581/alex",
lemmy_1     |       "actor": "https://enterprise.lemmy.ml/u/nutomic"
lemmy_1     |     }

According to Lemmy logs, the test suite responds with 400 Bad Request, but I dont see the actual error being reported anywhere.