This issue is caused by permissions restricted for the EvalExpert App, the camera can see but it cannot save images.
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Go to Settings > Apps (or Application Manager) > Permissions.

Then select the EvalExpert App and allow access 'Storage' access for the EvalExpert app.

NOTE: To get the most out of EvalExpert, we recommend allowing full permissions for the app - this ensures all features available in the app function correctly.