I hope you're having a wonderful week. The error message you're getting means an account, customer, item, vendor, or employee that you're trying to use has been made inactive. You can filter each of these to see any objects that you have made inactive. Here's how:
Filter Accounts for Inactive:
Go to the Accounting tab and choose Chart of Accounts.
Click the small gear icon on the right-hand side of the chart.
Check the Include Inactive box.
Filter Inactive Customers:
Select the Sales tab and hit Customers.
Press the smaller gear above the list of customers.
Push the box next to Include Inactive.
Choose the Sales tab and click the Funnel icon.
Under Status, hit Inactive and press Apply.
Go to the Expenses tab and select Vendors.
Navigate to the smaller gear icon and push Include Inactive.
Locate the Workers tab and hit Employees.
At the top of the Employee List, click the drop-down box, and press Inactive Employees.
Now you can use these steps to check which object(s) that you're trying to use are inactive.
Please let me know if this gets you back to business. I'll keep an eye out for your response.