As always, read the FAQ: https://wyday.com/limelm/help/faq/#useful-reports
You're using a particularly ancient version of TurboActivate. Upgrade to the latest version (again, that FAQ entry talks about how to determine the version you're using, how to properly upgrade, etc., etc., etc.).
Secondly, don't directly dig into native calls when we've written the wrapper. Use the interface as is.
So, after you've upgraded TurboActivate to 4.3.0, and upgraded the integration file (in your case, TurboActivate.vb -- again, see the FAQ), just call ta.IsActivated() and read the result (True or False). Also handle exceptions.
Follow the example.