Very odd! I've seen something similar happen when you generate an API while using Smartlead's trial version and once it ends and you upgrade, you need to generate a new working one. Does that sound like it may be the issue?
Ahh I see, actually I didn't get the right plan to use the API key.
So my next question is, can I download the table under a CSV and still use the different columns (LI post summary) in Smartlead?