I cannot check the box to see inactive customers.

Thank you for posting in the Community, @cm-yates.
 

Since you cannot see the inactive customers by checking the Include inactive box, please refresh your browser or sign out and log back into your account.
 

If the issue persists, I suggest using another browser like Firefox/Chrome or use a private/incognito browser. Using it will save data and prevent cookies from being stored on your computer.
 

First, open a supported browser and use these hotkeys:
Chrome: Press Ctrl + Shift + N
Firefox: Press Ctrl + Shift + P
Internet Explorer: Press Ctrl+ Shift + P
Safari: Press Command + Shift + N
 

If this fixes the issue, clear your regular browser's cache. It will help download a new copy of data, which will include certain functions in QuickBooks Online (QBO).

To stay current with our latest features and updates including, explaining cash flow, visit our blog: It's your journey. Were here to help.

Please leave a comment if there's anything else I can assist you, @cm-yates. I'll be glad to help. Enjoy your day and take care!