Lightroom Classic. All files are showing as 'missing'

All of my files in Lightroom Classic atre showing as 'missing' and int eh Develop module have the message 'The file could not be found'.  I followed the instructions in the Adobe Help to reconnect the images to the folders (which were not moved or relabelled) but when I have shut down and reopened the laptop (Windows) the links were broken again.  Any ideas or fixes would be much appreciated.  Thanks