“Unable to save 3471ee11-a65e-40d9-b54d-93129189f09f" We've had several reports of this. You will get this message when trying to register an LTI 1.3 tool on a Learn system when there is already an LTI tool on the same Learn system with the same domain.
One example: You register MyCoolRestApp on developer.blackboard.com with the domain: www.waycool.com. Now you register another, MyCoolLTI13App on on developer.blackboard.com with the same domain: www.waycool.com. You go to a Learn system and register MyCoolRestApp as an LTI 1.3 tool provider, then you try to register MyCoolLTI13App as an LTI 1.3 tool provider. You will see the "Unable to save..." message because you can not register two LTI apps on the same Learn system that have the same domain.