Difficulty with Client Signatures

Over the last few months, more and more of my clients have a hard time signing my documents. I haven't changed anything on my end. I'm not sure what the problem is because I can't see what they are doing. They can fill everything out, except actually sign the document. Also, is there a number to call someone for assistance at Adobe? I keep being sent in circles to try to find some type of contact information. 

Thanks in advance!