Don't animate every rig from scratch. Load a rig from your library, then use the Auto-Rig Pro Retargeting tool to copy motion capture data (from Mixamo or Rokoko) onto your library rig.
Fix: You likely downloaded a cracked version from a "free download" site. Cracked ARP rigs lack the Rig Library's code signatures. Purchase the official version. download autorig pro rig library blenderzi best
One common issue users face is a "Library not found" error. This usually happens if the add-on was installed incorrectly or if a cracked version has a missing library path. Don't animate every rig from scratch