I was playing with Canvas app in my Trailhead Play Ground (TP). I have implemented Canvas in TP successfully but very time I have received below error.
However, I have implemented same Canvas app in my Developer Org (DE) and getting proper output from Canvas.
Is there any known issue in TP regarding Canvas? Any idea how to fix it in TP?
PS: I was implementing Canvas app from below link: http://www.worldofsalesforce.com/2017/05/displaying-external-web-app-using-Salesforce-Canvas.html