Updating external list from sharepoint workflow - error

Question

I've created page workflow to update data in external list:

When I execute this workflow, I get an error. I don't know what causes the error:

I've read about permissions to the Sharepoint system account. I feel like I've tried everything. Do you have any ideas what can cause this error ? Is there any way of debugging such workflows in Sharepoint designer ? I've tried reading Sharepoint logs, but nothing interesting there.

TIA for any clues.

Answer 1

I've managed to do that, I needed to configure Secure Store Service application:

link 1

link 2