"The ZSC key or email address entered is incorrect. Please enter again."

"The ZSC key or email address entered is incorrect. Please enter again."

I am receiving this error when trying to connect to CRM from Invoice. I am copying and pasting my email and ZSC key from CRM, so it is not a typo on my end. I searched the forums and found a similar issue here: https://help.zoho.com/portal/en/community/topic/zsc-key-error-for-zoho-invoice-crm , so tried to connect to Invoice from CRM, but I don't have the option. I have options to connect to Projects, Support, Survey, Visitor Tracking and Advanced CRM analytics, but not Invoice. Please help!