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# Unable to load calibration.
### Explanation
This error message arises when loading a calibration file. It indicates that the selected calibration contains camera IDs that do not match those for the loaded videos.
### Possible Solutions
1. Check that the correct calibration file was selected. The calibration file may be incorrect for the loaded videos. Confirm that you selected the correct calibration file, which should have been generated using a calibration trial from the same data collection session as the loaded movement trial videos.
2. Check the camera IDs within the calibration file and the loaded video file names. If [Organize Videos](/apollo-v2024/theia3d-documentation/theia3d-dropdown-menus/tools-menu/organize-videos.md) is performed more than once to organize the video data and different delimiters or different parts of the file names were used to assign ‘Cam ID’, the camera IDs may not match between the calibration file and the loaded videos. If this is the case, the camera ID folder names for the calibration trial and movement trials should be changed to be consistent, and the camera IDs within the calibration file should be modified to match the camera ID folder names.
3. Check that the number of cameras in the calibration file matches the number of videos loaded. The number of camera views loaded in Theia3D and the number of cameras contained within the calibration file may not match. If the number of camera views loaded in Theia3D does not match the number of cameras listed in the calibration file, double check that you have selected the correct calibration file, that you are not missing any camera views from your loaded movement trial, and that the calibration file has not been modified.
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