No connection to the database of Access when using ODBC

In an Access application with 5 users, an ODBC is set up locally as a System DSN for each user. Since yesterday, one of the users got the message "No connection to the database". All other users could continue working normally.
The existing ODBC could no longer be edited, not even as an administrator.
I created a new DSN user already, but it doesn't work.