I don't know if the Wehrmacht or the SS even had gas at the front during the Normandy landings, but even if they had, they probably wouldn't have used it during D-Day, because of the weather. When the D-Day landings happened, the wind was coming from a westerly direction (see this weather forecast from june ut even if the weather was favorable, it would have been higly unlikely. u/Georgy_K_Zhukov gives a good explanation in this thread.

edited links and name.