Can drive but it is in 3rd gear, cannot shift gears?

The first thing I would do is check the transmission fluid level and if the fluid is burnt, I would do a fluid and filter service.

Automatic Transaxle Fluid

Type .................... MICHANG ATF SP-IV, SK ATF SP-IV, NOCA ATF SP-IV, HYUNDAI genuine ATF SP-IV or other brands meeting the specification approved by Hyundai Motor Co.

This guide can help as well, also we should run the codes to see if any are stored:

https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid

Here is a guide to help you get the codes:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Check out the images (below). Let us know how it goes.