If you stopped receiving Slack problem notifications from Dynatrace, check your Slack Webhook.
The Slack Incoming Webhook URL (created by the Slack admin) is specific to a single user and a single channel. If you're relying on a webhook tied to a deactivated account or channel, the webhook URL is invalid, breaking the integration, which means you no longer receive messages in Slack.
If so, ask your Slack admin to generate a new webhook URL using a valid account and channel. Once a new URL is generated, update the webhook URL in Dynatrace and test the connection. If you need a reminder on how to configure notifications, see Send Dynatrace notifications to Slack.