MSTeams contact webhook not work

Hello,

we have problems with MSTeams webhook contact, notifications not come to our MS Teams channel.

We test it also with test_alert.php and we get response status: 400

./test_alert.php -d -c 2

REQUESThttps://XXXX.webhook.office.com/webhookb2/XXXXX/IncomingWebhook/XXXXX
REQUEST STATUS[FALSE]
REQUEST RUNTIME[0.5199s]
RESPONSE CODE[400 Bad Request]

RESPONSE STATUS[400]
RESPONSE ERROR[Summary or Text is required.]

Thank you and best regards.