Cannot OK to create a joint - why??

[lure23]

Fusion allows me to build the joint and previews it in the animation. But the OK button remains dimmed.

Does anyone have a hunch what could be causing this?

More mysteriously. Now that I've jogged between the Screencasts and the browser, the OK is suddenly enabled.

A bug.

Fusion 2.0.6032, macOS 10.14.5

[lure23]

Interestingly, when the OK is dimmed, right clicking anywhere in the Fusion 360 Browser makes it enabled, again.