When I was attempting to write an answer today, I discovered that Circuitlab is no longer functioning--it just shows up as a blank white box over the page, and never loads.
The browser I'm using is Waterfox Classic (I can't use Waterfox Current for reasons that aren't relevant here), and though I do use ublock origin and noscript, neither appear to be blocking anything relating to Circuitlab (and no settings have changed since the last time I successfully used it, a few days ago).
If the circuitlab integration has been modified somehow (a patch or update or something) in the last week or two, something seems to have broken and should perhaps be double checked. If nothing has been modified on your end, then I dunno what's going on.