Download manager error - HTTP/1.1 401 Unauthorized; Class

Hi Experts/Gurus,

I have added 120 components in download manager and generated a stack through MOPZ.

I could download 70 components without any issue and now for the remaining components the error " HTTP/1.1 401 Unauthorized; Class: class dlclient.SMPIOException" is occurring.

all the pending components are partially downloaded. The error is repeating though I closed the download manager and tried again.

I don't see none of them as pending for approval.

why this error is occurring  continuously and  how to overcome and download the remaining components.

I will appreciate your help.

Thanks in advance