Hi @susmitha
The Secure Store Service is an authorization service that runs on SharePoint Server. The Secure Store Service provides a database that is used to store credentials. These credentials usually consist of a user identity and password, but can also contain other fields that you define.
To learn more about Secure Store Service, you could refer to:
https://learn.microsoft.com/en-us/sharepoint/administration/secure-store-service-planning
The "Claims Windows token Service” can only be accessed on the local server, so when you are using it, the service must be running on all of your WFEs and any other server that will access the external data. So I will suggest you to start "Claims Windows token Service” on WFE again.
For more information, you could refer to:
https://joshroark.com/sharepoint-facts-and-troubleshooting-the-claims-to-windows-token-service-c2wts/
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