Hey Mitch!
First of all, thank you for the purchase!
The Twitter error message is a known issue – they’ve updated their API and most of ThemeForest themes needed changes to their Twitter widgets. I’m in the process of updating the theme right now; meanwhile you can download the fix here, unzip it and upload into the following folder: /wp-content/themes/Fuji/includes/twitter-widget/, replacing the existing file. Sorry for the inconvenience!
Regarding the header slider:
– please make sure that the „Display custom header” checkbox is checked in the “Theme Options” menu, “Header” tab.
– choose one of the custom header types as the deafult one in “Content of the custom header”, same tab.
– this one is quite obvious, but just in case: make sure you’ve uploaded and saved the slides for the slider in the “Header Slider” tab ;)
You can read more about customizing the header on page 5 of the theme manual.
Let me know if this helps on the reported issues!
Sincerely,
Andrew | Satori