Generally speaking, here are some thoughts on how to get the best help with these issues.
First, and most important. YouTube makes constant changes to their API. Sometimes they will make a change that requires the TubeBuddy devs to have to push an update. So the first troubleshooting step should always be to check that you are running the latest version of the extension or app.
Second, if you are running the latest plugin, it will often help to uninstall, completely shut down the browser and reinstall the plugin. This helps clear cached data and often resolves the issue.