signal-cli-rest-api: Cannot send anything

The problem

After registering a number on a fresh container with no prior configuration I am not able to send any messages.

Command that was run:

curl -X POST -H "Content-Type: application/json" 'http://localhost:8080/v2/send' -d '{"message": "Test via Signal API!", "number": "<sender>", "recipients": [ "<recipient>" ]}'

And the response is:

{
  "error": "WARN  SendHelper - Failed to send message due to IO exception: Unable to parse entity\nFailed to send message\n"
}

In the container logs I am seeing:

[GIN] <timestamp> | 400 |    6.6703771s |      10.0.2.100 | POST     "/v2/send"

Are you using the latest released version?

• Yes

Have you read the troubleshooting page?

• Yes

What type of installation are you running?

signal-cli-rest-api Docker Container

In which mode are you using the docker container?

Native Mode

What’s the architecture of your host system?

x86-64

Additional information

I encountered this issue in all modes, i.e. normal, native and json-rpc.

Further, I have a version where a number was registered under version 0.64 and strangely when mounting this configuration directory, I can do everything without any problems…