It is essential that your Endnote Library is stored on your local hard drive. Do not store it on cloud storage services like OneDrive, Dropbox, or Google Drive. These services may corrupt your Endnote Library.
On University laptops and computers store your EndNote Libraries and Data folders at This PC > Windows (C:) > Username (e.g. MSM4)
Create back-ups frequently using the Compressed Library option (File > Compressed Library).
Store your back-up library in OneDrive and restore it to your hard drive if you need to at any time.
If you work between different devices you must synchronise your data via EndNote Online. If regularly synchronised, EndNote Online can provide an additonal backup of your Library.