This reported error is not uncommon and has been occurring since users starting sharing files on servers.
Option 1 - HowNow
Documents can be locked in HowNow by another person. If the document is saying it is 'In use' by another user, and you have checked that no-one has this document open, you can right-click in the document in HowNow, go into the Profile and Clear the 'In Use By' field.
Option 2 - Windows Systems
Alternatively you may have the issue where the document is held in the background by another process.
HowNow interacts with other applications through Add-ins and other background code to provide you with complex functionality.
When you have a document open, the application the document is open in often stores a temporary copy of the file in the background. This may be to perform part of a function or to save changes as you work within the document.
If you opened the document from HowNow the functions that HowNow performs will also need to interact with the document. Generally all of the applications and their functions manage to work well together.
Upon closing the document each application has to perform a function. This can take a little extra time as more applications are involved.
To avoid the following errors 'file is in use', 'file is already open', or similar, you can practice the following steps.
1. Save and close your document before closing the application
2. Wait for the document to close properly before performing another function on your PC
3. Avoid having too many documents and windows open at any one time
4. In complex documents, like Workpapers, wait until functions finish before starting others
To overcome this issue you can close the document that Windows still has open in the background.
>Open Task Manager, find the document still running, 'end task' this document. You should now be able to open the document again without the error.
Frequent occurrence of this issue may require an 'Office repair' by your IT team.
Your IT team may also be able to 'release' the document within your IT environment.