ORA-28575: unable to open RPC connection to external procedure agent

Check Oracle home path in listener file:

SID_LIST_LISTENER_EXTPROC =
  (SID_LIST =
    (SID_DESC =
    (ENVS="EXTPROC_DLLS=ANY,LD_LIBRARY_PATH=/pwrcard/home/usr/lib,MYPATH=/usr/bin:/pwrcard/home/usr/bin,APL_ENV_FILE=/pcard17/trace/env.txt")
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = /oracle/app/11.2.0/db_1) ---  /oracle/app/11.2.0/db
      (PROGRAM = extproc)
    )
  )