The error message you are receiving is because Excel requires that print titles be contiguous and complete rows or columns. This means that the rows or columns you want to repeat on each printed page must be adjacent to each other and cannot have any breaks or gaps.

To fix this issue, you will need to adjust your print titles so that they meet these requirements. Here are the steps to do so:

1. Open the worksheet you want to print and go to the Page Layout tab in the ribbon.
2. Click on the Print Titles button in the Page Setup group.
3. In the Page Setup dialog box that appears, go to the Sheet tab.
4. In the Rows to repeat at top field, click on the Collapse Dialog button (the small icon to the right of the field).
5. Select the rows you want to repeat on each printed page. Make sure they are contiguous and complete rows.
6. Click on the Collapse Dialog button again to close the selection window.
7. Repeat steps 4-6 for the Columns to repeat at left field if necessary.
8. Click OK to save your changes and close the Page Setup dialog box.

Your print titles should now be contiguous and complete rows or columns, and you should be able to print your worksheet without any issues.