I have the same problem. It is not on the login item list. I cannot delete the app because it says it is opened. It is not on the force quit menu. I can find a process with "ps -ef | grep Dropzone". I killed the process and try to start it from the finder it won't start. At one point I did see the "subscription" dialog and I clicked cancel because I wasn't sure which version I wanted.
I am on Monterey 12.3.1 M1 Pro.
Ideas?