Official comment
I am seeing that your account has 7 devices logged in. If you use the Google Play variant of the app and then install the 'b' or 'e' variants one device can show up as more than one.
You should have a device reset available in your account Profile.
https://support.dronesmadeeasy.com/hc/en-us/articles/4417374746388-Resetting-the-Authorized-Devices
If you continue to run out of devices you would need to upgrade your account to the Elite level to gain access for all the versions on all the devices you are trying to run.