A checksum is a calculated value used to determine that the file has not changed. If TakeOff thinks the file has changed because the checksum has, it will not be able to show the measures you've taken on it so far and to do more measures you will have to re-load the drawing.
Avoid making any changes to drawings which are in use in On-Screen TakeOff - this will include a change of the modified date, even if nothing actually changed.
Takeoff Checksum Error
What is a checksum? Why does TakeOff say the checksum on my drawing doesn't match? Why does TakeOff think my drawing has changed?
Written by Alina Stepanek