Trouble with a reciepiant signature

Hello,

   I sent a document that needed to be signed. Everyone was able to sign, until it went to the mother. She got a message 'na2.documents.adobe.com' she could sign but not submit. She said she thought it was waiting for me to sign, but I had myself last. Any help with trying to figure out why she cannot sign? When I opened up the 'in progress' document a very quick message flashed saying something about a network error, but to fast to read.