Discussion board where members can learn more about Integration, Extensions and API’s for Qlik Sense.
Have you checked that the machine you are connecting from is on the web socket white list of the server? The setting is found under the "Advanced" section of the virtual proxy settings in the QMC. You can find more information in the "Host white list" row in the table under "Advanced" at the following page:
No playground doesn't need any such white listing from your part. Do you get that message when trying to connecting to playground? Are you using anonymous mode?
It looks like you're trying to connect a QVF file on your local machine C:\....
Can you provide a few more details around how you're trying to connect? The more detail you can provide, the better.