Can you please share below information to debug the issue -
Please share fiddler logs while you perform the Request signatures workflow. Below are the steps to capture fiddler logs : • Download fiddler from: https://www.telerik.com/download/fiddler • Run fiddler and go to ‘Tools->Options’ • In HTTPS tab, ensure the checkboxes are checked: ‘Capture HTTPs connects’ and ‘Decrypt HTTPs traffic’. • Now let fiddler run and launch Acrobat and perform the same operation. • Once complete do a save of data by ‘File->Save->All sessions’. • Please share this data
Version of the Adobe Acrobat DC you are using? To check the version go to Help > About Acrobat and make sure you have the latest version 21.01.20135 installed. Go to Help > Check for updates.
As you have mentioned that you have changed the primary email address for the Creative Cloud, that is the reason you are receiving the error message.
On checking your account, I see that there was a free Adobe Sign account registered under your current Adobe ID. And when you changed the Adobe ID, it did not change for your Adobe Sign account.
In this case, I would suggest you get in touch with the support team as only they have the access to the backend settings and they can help you update the email address for the Adobe Sign account. You may reach out to the phone support team via the number provided for your region on this page: https://helpx.adobe.com/contact/phone.html.
In meantime, try switching back to the old Adobe ID (email address) and check if you can access the service.