1. Check your document settings – Ensure that column breaks cannot be deleted, and confirm the paragraph setting.
2. Check paragraph settings – Confirm that the column breaks cannot be modified.
3. Check document properties – Ensure that column breaks are set up in the document.
4. Check your page layout settings – Ensure that column breaks are specified in your page layout.

If all the settings are correct and column breaks still cannot be inserted or altered, then it may be due to formatting constraints within the document or a particular section of the document.