Editing and modifying text in scanned document

Hi,

I used to edit text of scanned documents with acrobat pro and it was working perfectly. Now I have acrobat DC version and I can't get acrobat to identify the text in the pdf. I don't understand because the option "Modify text and images in the pdf file" are available on both versions.

I tried with "tools", "scan&OCR", "Enhance", "Recognize text" but it doesn't seem to work neither.

I can modify text only in high quality pdf.

Do you have any idea why ?

Thank you very much !

Regards,