We have an issue trying to set a multi-select parameter in ssrs-2016 via the Manage->Parameters menu in ssrs-2016 itself. parameter has available values, it works in the report normally. but when going into set some defaults via the ssrs website, the available listing is blank. is there something that I am missing?
What I find interesting is that the rendering of the list in the report looks very much like it hasn't changed from ssrs-2008 r2. I have tried creating a new report with just a single report parameter and I get the same thing.
You can type the default in, like with the other parameters by clicking in the location circled, typing it in, and hit enter.
If your looking to see all the drop down options, you will have to run the report to get those, and once you have one picked out, type it in, like described above.
Hope this helps.