This error message (seen above) occurs if you are attempting to upload a document that is no longer checked out by you. Often becuase it is an older version of the document that you have already saved to the system or because the chapter was unlocked before you saved it back to the server.
For the sake of document integrity you can only upload the exact version that you downloaded – and only if it is checked out by you. This is indicated by a red padlock icon on the page where you check the document out:
Because the document is not checked out you will not be able to save it back to the server. To work on the file you will need to download it again using, "Edit chapter". If you continue to have problems please contact support.
In rare cases this error indicates a network issue where our server cannot be contacted, such as no internet connection, an unstable network or a security setting.