Shailja - If you look at Background Tasks for Extracts do you show these extracts failing? What does the status show?
So with the web connector the error is "..None of the workbook's data sources are refreshable.." (attached)
For Simba driver, looks like the default timeout for queries is set to 600 secs (we are changing it to the max 9000 secs now)
For Terradata, looks like the driver was not installed properly, so we will take a stab at that again.
Will update this thread with the results of the changes.
Thanks Doug for your suggestion, helped a ton!