Impossible to launch the sub-groups discussions I've programmed in advance

I've programmed several times my sub-groups composition in advance (via the website in the advanced option, entering each e-mail adress in each rooms and when I launch the break-up groups not only the rooms I've created don't oppen but moreover , even if I close all the rooms I can't use the automatic dispatch anymore which is really a nuisance !!! As anyone met this problem before and can explain how to avoid that... truly if this can't be fixed I move to Teams...as this is one of the major point of difference with Zoom (but if it doesn"t work then why bother ?)

Thanks in advance for your help (ideally in French as I'm on the French Zoom version but I can manage with ENglish hopefully...