CE Pets not working anymore in WoW Classic?

I’ve not logged into WoW Classic in a while, but I just did and for some reason my previously working Collector’s Edition pets (in this case Panda Cub) can’t be summoned? When I click it to summon, all I get is “Can’t Add Companion To Your Account”. Is this a bug with the pet? Like I said, it was working fine last time I played.