Hey Dominika,
Could they try clearing their cache/ cookies for Dovetail specifically and try logging in again? Steps below:
Right-click anywhere on the page and choose “Inspect.”
In the panel that opens, click the “Application” tab.
Under “Storage,” you’ll see sections for Local Storage, Session Storage, and Cookies.
For each one, right-click on the site name (or any listed items) and select “Clear.”