It's not real clear what "does not work" means.
If it's access to the report, It looks like the biggest problems may be understanding that data source credentials is separate from permissions to access a report.
SSRS uses the data source credentials to connect to the source of the data and obtain the data for the report.
Permission in Report Manager is what is used for access to the report. For everyone to have access, you can grant access to the authenticated users group. Everyone group would include authenticated users, guest, built-in accounts such as service, local service, network service, etc. How you do that depends upon how you are setting up security in general for the reports, folders, etc.
If it's something with the shared data source, what is the error message, what is not working?
If it's something else, we would really need more details.