Hi Lars, Richard here.
Thank you for contacting MongoDB Support, I am happy to assist you with this issue.
If you dont have any tools to connect you could add an IP address also to resume your Atlas Cluster,

Select Network Access on the left of the Atlas UI to add IP Access List Entries for your project.

Hit ”ADD CURRENT IP ADDRESS” to add your current IP address:

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or add 0.0.0.0/0 to allow access from everywhere for testing.

Note: Security Features and Setup is at Project level.

You need to be a Project Owner to Configure IP Access List Entries.