You know what, I have also faced this same issue recently and resolved it using below tricks/tweaks.
First of all below are the prerequisites of using Business card scanner in Model driver app/UCI application.
Make sure you meet above prerequisites and now regarding the issue you are facing, from 1 of the Microsoft's official documentation on Business card setup I have found that I was missing 'Cleaned Image' property setup. This property must be set to single line/multi line text field through which you are scanning Business card. Example – if you have utilized OOB field of Business card scan then set it to 'businesscard'.
Here is the documentation which I had referred to – https://docs.microsoft.com/en-us/ai-builder/business-card-reader-component-model-drivenThis answer is provided by Kishan Modha, Software Engineer, Dynamics CRM, Synoptek
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