You might check the below points. I haven't encountered this so not sure if these suggestions work
Clear the AEM cache and ensure that no content is locked. You can try restarting AEM to refresh the cache. Also, verify that there are no content locks by checking the CRX/DE Lite.
Ensure that the user or service account making the API request has the necessary permissions to access the content.
Check the AEM error logs and the error.log file for more detailed information about what might be causing the issue.
Verify the form components and ensure they are configured correctly. Review any logs related to the Adaptive Forms component for errors or warnings.
Check the configuration of your AEM instances to ensure that they are aligned, especially with respect to content versions and replication