My Lambda shows Access denied

This issue of not being able to access Lambda functions as a root user and encountering "Access denied" messages is not uncommon. There are several potential reasons for this problem:

1. Region Check: Ensure you're in the correct AWS region where your Lambda functions were originally created, as Lambda functions are region-specific.

2. Temporary Account Block: Your account may have experienced a temporary block due to a suspected malicious access attempt, causing functions to become temporarily inaccessible.

3. Service Health: Check if there are any ongoing issues or outages with Lambda in your region using the AWS Service Health Dashboard.

4. Browser/Device Issue: Try accessing your Lambda functions from a different browser, in incognito mode, or from a different device to rule out any local issues.

5. Organizations and SCP: If your AWS account is managed by Organizations, check that Lambda operations are not prohibited by Service Control Policies (SCPs).

Since you're experiencing this issue as a root user, it's likely there might be a problem with your AWS account itself. The recommended solution is to contact AWS Support directly by opening a support case under the "Account and billing" category, which can be done free of charge. AWS Support will be able to investigate any account-specific issues causing this problem and provide you with a resolution.
Sources
Root User - Lambda Functions are Gone! | AWS re:Post
Access denied in creating lambda function | AWS re:Post
Not able to see my lambda functions | AWS re:Post