For Collaborate plans, you can simply re-add your client the same way you did before- by sending them an email invite again to their email address, or by providing them a hyperlink. You can view details on how to go about this on this help page here: https://help.eatthismuch.com/help/etm-professional-manage-clients-guide 

For Control plans, please send us an email at [email protected] to request your client be added back to your account and we will take care of this for you from our end!