Hi Fay

Thanks for posting in the Community!

To access Revision History you will need to select the clock icon from the menu bar at the top of your document.  Alternatively you can select Revision History from the File menu. 

Once in the Revision History please click on one of the tiles located on the right-hand side of your screen to view the corresponding document version.

The following help documentation explains everything there is to know about revision history: Revision History

Note that if you open a version and click Restore you will return the document to the previewed version removing all edits made in between that version and the document’s current state.

If you are unable to view a previous version it could be that you (or a collaborator who has edit access to the document) may have restored the document to a specific version. This would affect the document on all collaborators' accounts including that of the document owner.

It is however possible to return to the latest version of your document (prior to a restoration). To do so you will need to restore your document to the most recent version in your Revision History menu.

If this does not help I would recommend that you file a support request via this link so that we can take a closer look at the situation you are encountering. Please make sure that you include the following information:

* The URL of the document

* The time (and time zone) you opened your document.

* The time you closed the document.

* Which edits were not saved.

* A detailed account of the time frame when you noticed your edits were not saved.

Thank you!