Hi Pablo,
Can you please rename the system alias property of system object to SAP_SRM instead of SAP_SRM_1 and then try to re-register the webflow connector in UWL.
From the screenshots, I could see that you've created a system alias SAP_SRM_1 but in UWL you've specified SAP_SRM as system alias which could be the cause for this issue.
Also, please ensure that you've created a RFC destination in NWA.
If it has not been created, please follow the SAP Note : 1133821 - UWL Destination Service configuration.
BR,
Anurag