Found a solution. You must have Samsung app called SMART HOME connected to the robot. Enable in the Alexa app and then device discovery in Alexa app. If you have the newer app Samsung SMART THINGS that fine but it does not work with Alexa as the app see it as a switch. SMART HOME see it as other. I use the SMART THINGS because it works well with my washer, dryer and schedules when the robot vacuum to come on. If you have both of those apps enabled in your Alexa app, you need to delete the duplicate robot device. The one that you need to delete is the robot that works through THE SMART THINGS on the Alexa device screen. Once you have the robot listed once on Alexa device page tied to SMART HOME you are golden.
I'm having the same issue. Unforunately, when I attempted to use SMART HOME, I get a message that it is being discontinued and to use SMART THINGS which does not seem to work to connect my R7070 to Alexa.
Nevermind... I found my issue. Although I was using the SMART THINGS app on my phone, I had enabled the SMART HOME skill in Alexa. Once I found the matching skill, it worked. Perhaps others have made the same easy mistake?