Attachment Upload Fail in CRM

Attachment Upload Fail in CRM

I am unable to upload a PDF attachment to a contact in CRM. 

CRM attempts to upload (blue loading bar), and then states "upload failed." 

I have restarted my browser and computer. I also tried to save the file as a JPG and the upload still failed.

I checked and our account has plenty of storage available. I have been able to perform this function MANY times before. Please help.