I might be misinterpreting your issue but remember that the only way you can have 2 companions at the same time is if one is humanoid and the other non-humanoid. Rex and Ed-E are the only two non-humanoids.
If it's a case of a "lost" companion, one confirmed fix is to use the elevator at vault 22 and your companions will be waiting for you when you exit. You need a repair skill of 50 to fix the elevator first though.
by "dismiss" do you mean telling them to "wait here" or by telling them you should part ways?
I'm trying to recruit cass and I have boone and ED-E "waiting " back at the motel in Novac. I just completed Boone's quest, so should I just part ways with him? If I do, can I get him back at some other point in time?
Life is a first-person adventure. Procrastinating since tomorrow.
^ You have to part ways with him, he'll go back to novac and you can get him at any time. I'm having the same problem as the OP, as I know I don't have any followers with me and for some reason Arcade wont come with me but I can get anyone else to follow me. It has nothing to do with my karma or anything as I did nothing different except take over the Lucky 38. I'm still ranked as a lvl 33 messiah and have done nothing negative to anyone but the legion lol. For some reason I just can't get him to follow, he makes some remark about having a menagerie of followers with me and I get the "you can only have 1 follower at a time message". ITS IRRITATING