r HTML visual widget - Plotly elements have suddenly stopped working across multiple visuals

And just as suddenly, they've all started working again. No change to anything and didn't even have to close Power BI desktop to get them working again on there - just switch report pages to force a refresh. The same thing had not worked all morning. 

I'm glad they're back, but I'd be interested to hear any theories people have on why this happened as I'm still stumped and would like to be able to give a summary of what happened to the users of our reports.

My only theory at the moment is something to do with plotly loading a file from the web and this temporarily being blocked (or plotly itself being down for some time so said theoretical file couldn't be accessed, though I couldn't see any evidence of this when I looked at their status page and generating plotly graphs using R outside of Power BI seemed to work fine).