Electronic Signatures Approval Page flashes after Approve Button

Summary:

I've followed https://docs.oracle.com/en/cloud/saas/readiness/scm/26a/maint26a/26A-maintenance-wn-f42293.htm

But when it comes to the popup window for Approval, after clicking Approve, it prompts to log in again and after that the screen 'flashes' and nothing happens.

I've verified that the electronic signatures privilege is in the custom role and provisioned.

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