Hmmm I can’t think what would cause that. Only one thing comes to mind… perhaps all the files didn’t get extracted properly.
Please try downloading osTicket-1.14.3-Awesome-101.zip from the Downloads page and extracting it again. Overwrite the directories and files in your osTicket Awesome installation directory with the newly extracted files.
If you would like my assistance I am happy to take a look and get you sorted if you fill out this form with as much information as possible.