Customer information Is sub-customer error?

Hi subaramani201084,

Thanks for sharing the error message you received. I'm here to help you get past this issue. 

Sometimes, data stored from your regular browser for a long period causes unusual behavior to the browser. Let's access your QuickBooks Online (QBO) account via a private or incognito window to see if this a web browser-related issue. 

Here are the shortcut keys on accessing a private or incognito window:

• Google Chrome: Ctrl + Shift + N
• Internet Explorer: Ctrl + Shift + P
• Mozilla Firefox: Ctrl + Shift + P
• Safari: Command + Option + P

If that works, we'll have to go back to your regular browser to clear its cache. This will give your regular browser a clean slate and prevent unusual behavior in the browser.

If the issue persists, I suggest using another web browser.

I've also added these great articles on adding and managing customers for additional reference:

• Add Customers
• Edit customer information
• Add and manage customers in QuickBooks Online

I'm always here to help if you need further assistance. Take care.