Edit button in interactive code does not appear to work

When I click `Edit` in active code, the button text becomes `...`, but I am not able to type in the code block, either on Firefox 61.0b5 or Chrome Version 66.0.3359.170

Reproduce the issue by opening an active code block and clicking Edit in Firefox or Chrome, as reported. Inspect the interactive code editor entry point and the transition where the button changes to `...`; done means the code block accepts typing after clicking Edit in both browsers.

Written by the indexing model from the issue text.