The Free On-line Dictionary of Computing (19 January 2023):

PEBCAK
PBCAK
PBKAC
PEBKAC
PICNIC

    (Or "PEBKAC", "PBCAK", "PBKAC") Tech support
   shorthand for "Problem (Exists) between Chair and Keyboard".

   An alternative is "PICNIC" - "Problem In Chair, Not In
   Computer".

   An acronym commonly used by helpdesk technicians to indicate
   that a problem is due to the user rather than the system.

   See also UBD.

   (2012-08-26)


The Jargon File (version 4.4.7, 29 Dec 2003):

PEBKAC
 /peb'kak/

    [Abbrev., “Problem Exists Between Keyboard And Chair”] Used by support
    people, particularly at call centers and help desks. Not used with the
    public. Denotes pilot error as the cause of the crash, especially stupid
    errors that even a luser could figure out. Very derogatory. Usage: “Did
    you ever figure out why that guy couldn't print?” “Yeah, he kept cancelling
    the operation before it could finish. PEBKAC”. See also ID10T. Compare 
    pilot error, UBD.