Hi @steve_corey,
Start by decoding the KS to see what attributes it holds. You can that by going to Admin Console->Developer->System Helper, pasting the KS string in “String to manipulate” text area and checking the “KS” radio button.
If the reason for the error is unclear by the results, you’d have to look into the code that generates that KS.
I don’t know whether you’re using the session->start() action to generate it or a local function in the client lib but this can make a difference. Perhaps someone deactivated the partner ID in question?
You should also look inside the /opt/kaltura/log/kaltura_api_v3.log. Of course, if you have several API nodes, you’ll need to look at each one in turn and search for erroneous patterns.