This article will cover how to remove stored X-docs user credentials

X-Docs - Problem with Opening Word Documents 

Error message received trying to open document in X-docs

"No access. Contact system administrator".

Try removing your credentials stored in Credential Manager

Close browser and office

Remove any stored X-docs user beginning with MicrosoftOffice16.. found under Windows Credentials

(Multiple entries can sometimes be found)

You can do this via control panel as below:

When credentials are removed, open X-docs and try and open a document and if prompted. Add credentials and login.

Check Word Account is not set to the wrong account

If this didn´t help, please contact support