The exclamation mark indicates that a test, component, or file that is associated with the solution is not in the same location that it was when it was added. This is often caused by moving tests or resources from their original location in the file system or the ALM test plan tree. Can you check if the original file has been moved? If possible, can it be put back, or you could make a note of what the file is and delete it from the solution explorer, and then add it back again from its new location.

In some instances, if the test, component, or file has become corrrupted, UFT will also flag that as an issue, but this is not very common.