Apprise notifications sending issue: bad request

I cannot send Apprise notifications anymore, with French content.

Every try results in:

[2021-11-23T08:59:33.745] [ERROR] notifications - Apprise HTTP error:  Http request failed with status 400: Bad Request
[2021-11-23T08:59:33.746] [ERROR] helpers - when trying to send a notification: Couldn't send notification with apprise
[2021-11-23T08:59:33.746] [INFO] helpers - Error
    at new KError (/home/user/app/build/server/helpers.js:59:22)
    at /home/user/app/build/server/lib/notifications.js:95:19
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
    at async Notifier.sendTestNotification (/home/user/app/build/server/lib/notifications.js:100:9)
    at async sendTestNotification (/home/user/app/build/server/lib/notifications.js:160:9)
    at async testNotification (/home/user/app/build/server/controllers/instance.js:87:9)
[2021-11-23T08:59:33.747] [ERROR] HTTP - POST /api/instance/test-notification - 500 (7 ms)

I tried locally with curl -X POST http://localhost:8080/notify -H "Content-Type: application/json" -d '{"body": "Content", "title": "Test notification", "urls": "gotifys://************"}' and I received the notification, so my Apprise API server runs fine.