REST API: Error 404 when sending POST (cURL)

Hello Redmine-Professionals,

I'm always getting ERROR 400 when sending an POST curl Statement.
The Picture is in the Attachments.

cURL Statement:¶

curl "https://[Path to XML]/issues.xml" \
  -X POST \
  -d "[XML-Code]" \
  -H "X-Redmine-API-Key: [API-Key]" \
  -H "Content-Type: application/xml"

<?xml version="1.0" encoding="UTF-8"?>
<hash>
  <status type="integer">400</status>
  <error>Bad Request</error>
</hash>

Thank you!

Error