Thanks for helping.
My experience service URL is https://hzwwdfyk.studio-trial.thingworx.io
So, I tried to access by https://hzwwdfyk.studio-trial.thingworx.io:8443/Thingworx/Composer
resulting in error.
hzwwdfyk.studio-trial.thingworx.io’s server IP address could not be found.
Try running Windows Network Diagnostics.
@rsingaram: It seems instance service is down which could cause this issue. Checking internally with DEVOps team to restore the service or see if there is any other issue.