According to your description, I have the following questions to confirm with you:
1.Does anyone else have the same problem in your organization?
2.Did you do any operations before this issue occurred?
If your channel is deleted, you can recover it within 30 days. The following steps show the process to restore a deleted channel.
- Click More options next to the target team > choose Manage team
- In the management page, open Channels tab and expand the Deleted list > Click the Restore button.
- You can check Deleted channel activity in audit log from Microsoft 365 compliance as below. Choose a suitable Date and time range and Deleted channel activity.
- Then, click Search button to retrieve the related event.
Meanwhile, you could check Teams web client . If there is no problem in Teams web client ,we recommend you delete Teams cache file client and restart it. For more details about how to delete Teams cache file, you could refer to this link's step.