At any time that a file is opened as a 'non-GLP' file, any previous GLP status will be annulled. This is flagged up by the status lights in the top left of the LabChart view where the GLP status is shown.
Whilst it is possible to save a signed file where you have opened a non GLP file and made modifications, it will show in the Audit trail that a non-GLP file was opened and still the status will not revert back from Non-GLP document. Only files that have been open, saved, reopened and re-signed as GLP files will have the GLP Document status in the file.
For further technical assistance with this or any other issue, please contact ADInstruments Technical Support by clicking HERE.