PDF forms not importing into response file

I am using Adobe Acrobat Pro XI to create fillable forms and collect responses. I have collected a large handful of forms and only half of them are importing properly into the response file. The other half give me this error message "Acrobat could not collect data from the file [FileName.pdf] into this response file. Either it is not a valid form that was completed and returned to you, or you don't have access rights to it.

When I open the PDF itself in Acrobat Pro, I have not problem viewing the contents. However, it seems like it is not recognizing the sections of response fields that have text in them. I am not sure if that makes sense.

I think there may be issues with some people filling out their forms on Mac and I am using Windows, but I need a solution that will allow me to meet everyone's needs.

If anyone can suggest troubleshooting options or provide support, it would be most appreciated.

Thanks!