When opening the inbox, interaction quite often is not available other than scrolling.
The send tab never is available for interaction. No highlighting, hence ability to click any buttons. It seems that opening the global rules frame before anything else after login/reload usually allows interaction. The global rules often suffers the same problem.

What version of the product are you using?
3.0.0 and 3.0.2 of Inbox

Do you have an error log of what happened?
No erros. Iirc there was a parent frame doesn't exist or something of the like with older libraries. Will attempt to reproduce if possible.

Please provide any additional information below.
As said, reload and open global rules from fubar plugin immediately usually allows input for global rules and inbox.