One account can be invited to join one company only, so you cannot invite a colleague who already has a FangCloud to join your company. You can solve this problem with two solutions: 1. You may invite another account (mobile phone number/email) of your colleague that hasn't been registered on FangCloud to join your company. 2. If your colleague no longer needs the registered account, you may ask him/her to cancel it (Entrance for account cancellation: Enterprise Settings - Enterprise Information - Cancel). After cancellation, you can invite him/her to join your company again.