Sometimes, when you insert a cross-reference to a paragraph, the first word in the paragraph is conditional. The cross-reference marker that FrameMaker inserts then also becomes conditional and takes the condition tag settings of the first word. This marker is hidden when you hide the conditions of the first word. As a result, if the condition-tag settings of the cross-reference and of the cross-reference marker differ, you end up with a mysterious unresolved cross-reference!
Consider the screenshot below. Here, the first word in the cross-referenced paragraph is conditional. However, since all conditions are currently displayed, the Cross-References pod in FrameMaker 9 shows the corresponding cross-reference as resolved.
Now, consider the illustration below. Once the condition for the first word of the cross-referenced paragraph is hidden, the Cross-References pod indicates that the corresponding cross-reference is broken.
To avoid this situation, select just the cross-reference marker at the beginning of the source paragraph, and make it unconditional. This way, the marker will always be visible. The cross-reference will now be resolved regardless of the conditions visible.
See this Help article to understand how you can apply or remove conditional tags to text. For greater insight into issues that you may face while working with conditional text, see this overview article, especially the Planning conditional documents section.