Hello, olegnay.

Thank you for reaching out to the Community. If you are experiencing issues with your QuickBooks Desktop, like missing data, it is possible that your data is corrupted or broken. To troubleshoot this issue, you can try the following steps: 

1.  Run the QuickBooks File Doctor tool: This built-in tool can help you diagnose and fix issues with your QuickBooks company file. You can access it from the QuickBooks Tool Hub or by downloading it from the Intuit website. 
2.  Verify and Rebuild Data: This is another built-in tool that can help you detect and fix data integrity issues. To use this tool, go to the File menu in QuickBooks Desktop and select Utilities > Verify Data. If QuickBooks detects any issues, it will prompt you to Rebuild Data. 
3. Restore a backup: If the issue persists, you can try restoring a backup of your company file. This will allow you to go back to a previous version of the file when it was working correctly. Be sure to create a backup of your current file before restoring a backup. 

On the other hand, to find which vendor or customer has unsupported characters in QuickBooks Desktop, you can use the following steps:

1. Go to the Customers or Vendors menu in QuickBooks Desktop and choose Customer Center or Vendor Center. 
2. Click the Excel button at the top of the list to export the customer or vendor list to Excel. 
3. Open the exported Excel file and select the column that contains the name of the customer or vendor. 
4. Click the Conditional Formatting option under the Home tab and choose New Rule. 
5. In the New Formatting Rule dialog box, hit Use a formula to determine which cells to format. 
6. In the formula box, enter the following formula: =IF(SUMPRODUCT(--ISERROR(CODE(MID(A1,ROW(INDIRECT("1: "&LEN(A1))),1)))), "Unsupported," "Supported") 
7. Press the Format button and select a color to highlight unsupported customer or vendor names. 
8. Click OK to close all dialog boxes. 
9. Save the Excel file and import it into QuickBooks Desktop to update the customer or vendor list. 

However, if none of the above steps resolve the issue, you can Contact QuickBooks support for further assistance. They can provide additional troubleshooting steps or help you repair your company file.

You can visit this thread whenever you have additional questions about unsupported characters. I'll be around to assist further. Have a good one.