Google alert webhook integration

I work with Google Big Query. I set up an alert that would be sent if no data appeared in the table for a certain period. I want alerts to arrive in a specially designated channel in the mattermost in the form of messages. I got the required webhook and entered it into the webhooks field in the data retrieval channel. Google cloud sent a notification that the integration was successful “Test notification successfully sent. Please manually check the receiving end.” However, there are no notifications in the mattermost channel and nothing has arrived there. I tried changing the channels, making them open and closed, but this did not lead to results. Perhaps someone has encountered similar problems, please help! I will be very grateful!

What do the Mattermost logs say? If nothing at first, try enable debug logging