cannot add books

continue to get this message on Calibre version 3.39 and 3.23.

Failed to start worker process
Traceback (most recent call last):
  File "site-packages\calibre\utils\ipc\pool.py", line 201, in start_worker
  File "site-packages\calibre\utils\ipc\pool.py", line 189, in create_worker
  File "site-packages\calibre\utils\ipc\pool.py", line 73, in start_worker
  File "site-packages\calibre\utils\ipc\simple_worker.py", line 167, in start_pipe_worker
  File "subprocess.py", line 394, in __init__
  File "subprocess.py", line 644, in _execute_child
WindowsError: [Error 5] Access is denied

uninstalled, reinstalled, restarted with no resolution. OS isWindows 10. suggestions?