This typically indicates an issue or fault with the AC adapter. The specifications of this AC adapter are not unusual and a suitable replacement maybe found at an electronics retailer.

The PSU specs and barrel connector dimensions are as follows:
Output: 12 volts DC 1-2 A (1000-2000 mA), center pin of barrel is positive (+)
2.1mm ID, 5.5mm OD

If you’re unable to source this, a replacement can be purchased from Apogee within North America or an Authorized distributor outside the Continental U.S.