I do not understand this question:
registration dies not need a customer ID (it is not mandatory)
Users WITHOUT customer Number, the System cannot give additional rights f.e. show allplan licences or the Support contract Infos for paying customers
Users WITH confirmed customer Number, may see allplan licences of this Office and additional the Support contract Infos
PS: also in your Accoutn there is no Allplan Customer ID, so you can see: registraiton works without.
to be able to SEE YOUR projects, the user needs an inviation from your team, send out by teammanagement tool in bimplus.