Error Message Connecting to SharePoint

I haven't had any problems connecting to my sharepoint server, but this morning I'm getting a strange error with the Report Plus app on my IPAD:

Authentication Fails

The operation couldn't be completed. (DDXMLErrorDomain error1.)

Is anyone else getting this error?  Connections to sharepoint work fine from other apps on the same ipad and other ipads we've tested with are having the same problem with ONLY this report plus app.