To fix the user's issue you will have to do the following steps
Create a new user in Dimensions, ensuring that the email address is entered.
Depending on the version of Dimensions, it may also be necessary to tick the Access Evo user option in their record settings.
Create an Access Evo user with the same email address
The article Access Evo: How to add new members shows how to create a new Access Evo user.
Give the new use privileges to Access Document.
Details of how to give the member access to the Document role can be found in the article Access Evo: Manage member roles