Just a guess here, but the temporary url is an object, not a string. If you’re trying to pass the object itself, that probably won’t work. The network protocol understands only some basic data types, not arbitrary object types. See Valid arguments and return values.
The good news is that you can extract the url string from the object, so you could pass that instead. Follow Stu’s documentation link, above, for TempUrl, and read to the bottom. You’ll see how to extract the url string from the object.