Yes, I have a fully running Robo Tank on version 6.6 that I attempted to upgrade but couldn’t. It still works fine on 6.6. I took a second card and cleaned loaded it on a second raspberry pi and robo tank. The 6.7 will not control either power bar on either controller. The 6.6 card works on both.Have you placed the jumper leads for the ac bars on the main controller. These need to be placed before the ac bars work. You can also place a safety float switch if you want the backup.