Some versions of Acrobat show document as locked.

We are encountring some documents that will not load to our digital signature providers's cloud - OneSpan.  We are being told it is because they are locked.  We are not showing it as locked in our versions of Adobe Acrobat Pro and Adobe Acrobat Pro DC.  They insist that it shows the document assembly and page extraction as locked when they view it with their version of Adobe Acrobat.

This has occurred multiple times, with different documents.

Does anyone know how this could be occurring?