SQL Authenticated Account is unable to select a View in MS SQL Server
If you check the How to Create a Linked Server doc, you'll understand that your current configuration works like this:

Be made using the login's current security context Specify that a connection will be made using the current security context of the
login for logins not defined in the list. If connected to the local
server using Windows Authentication, your windows credentials will be
used to connect to the remote server. If connected to the local server
using SQL Server Authentication, login name and password will be used
to connect to the remote server. In this case a login with the exact
same name and password must exist on the remote server.

Since your SQL Server login doesn't exist on windows you can't access the file. You should create a mapping to that specific login defining a remote user and password with permissions on that server to read the file.
Just beware that anyone logged in SQL Server with that SQL Server user will have the privileges of the Windows login you defined on the mapping.