I just purchased the Membership plugin. I wanted to do a test install on a sandbox site before rolling it out to the production site. I installed it on the sandbox and then it worked.I then installed it on the production and since it is the single license it is saying it's installed somewhere else. I then followed the directions of removing the sandbox domain in the licensing so only my production was there. Still the upgrade/update is not working. Can you please set my account so I can use the Membership plugin on this domain: http://interactivediversitysolutions.com
Also, are all your plugins only one domain use?