Note : Zoho Service Communication (ZSC) Key Generated by following this article

What i did :

• Login in CRM
• Click Setup
• Apps & Add-ons
• Click on Zoho Invoice/Zoho Books
• Two buttons display configure Zoho invoce and configure Zoho books
• After select any of them asking for email address and ZSC key

Here is the issue, when i put my email and zsc key, it show the error Internal Process Error

Please help me i m new in zoho, guide me if something miss-configured.