The search command is not correct.
COMMENTDATE%3E%3D20200919 AND NOT K%3D%27Hilfsr%C3%BCckz%C3%BCger%27 AND A%3D%27Wainwright%2C Joseph C. J.%27 AND G%3D%27s%23%27 AND CPLUS
atomic expression must have form 'field = value' [COMMENTDATE % $$NUMBER0 E % $$NUMBER1 D20200919]