I can not add new worker anymore

Hi - Im just beginer. I’m trying to add worker. There was no problem with GPU one. Then I delete worker. I did this several time. Now I can not add worker any more. I can just download rig.conf file, but then system do not generate any rig any more - still coming back to the beging asking to create new worker. And it is in circle. Can anyone help? Does it means when I exceed 4 of them I can not add anymore. It is ok, but I deleted all of them - I have noone at this moment in my farm