Try following:
- logout from your site admin area (login first if you are not logged in)
- login into joomlapolis
- login in to your site admin
- go to CB install - install from web
- click the small refresh button at bottom right

That should allow you to install again.

Please confirm if the above solves your issue, as we are always trying to improve the user experience.

Something installed on your Joomla site or computer it self is likely breaking the JSONP request in that case. The way JSONP requests work is it allows cookies to pass and function on the called domain. This allows the install from web endpoint to correctly see you're logged in. It's possible your browser or even a browser extension is blocking the cookie usage. Have you tried a different browser?

Nope, not possible to work without JSONP request. The only other option is a cross-domain POST to log you into Joomlapolis, which we've no plans of doing. We've considered a web API Key, but then it's too easy for people to share the keys with others to circumvent needing a valid subscription (the install from web cache is only active for 24 hours), which unfortunately would happen. Will review this further as we maybe able to implement web API Key usage by requiring the domain to be supplied in advance, which would help reduce sharing.

forge.joomlapolis.com/issues/7197

Note there is no guarantee this will be implemented. I don't forsee any issues implementing the functionality in package builder it self, but whether we use it or not will have to be discussed internally. We will have to discuss the risk assessment of doing this. We want install from web to be convenient, but we don't want 1 person sharing a key for example to 20 people; that wouldn't be good for our business model.