Tick boxes completed on the agreement not showing up when signed and filed

Hi All, 

I send fillable forms to request e-signatures. The recipient is required to fill in several tick boxes to accept agreemtent of T&Cs and then they sign the document which is returned as 'filed and signed'.  They do complete the tick boxes which show as a black tick when they do. However, once signed and filed it does not show any of the boxes have been ticked, although I am not clear on whether the tick maybe showing up as a white tick? The same applies when the document is downloaded.

I had done the April update and uninstalled and reinstalled Adobe Acrobat with still no success in resolving this issue.

Any thoughts, as this is integral to our agreements.

Thank you