No image files found in selected input folder

[al9alal]

Hello and hope this post finds you well.
Thank you very much for this great and highly needed software.
I tried using it in an exam but encountered an error of: "No image files found in selected input folder.
Using 150-question form variant."
I tried saving the scanned forms images in png, jpg, bmp, pdf but all gave the same error.
Even when I tried to save the sample pdf and image files in the folder it gave the same error.

Is there a solution for this issue?
Thanks again for all your efforts.