i know this was a year ago, but if shrek doesn't move on the map you're playing in, Then the map most likely has no navmesh, you can generate one by opening the console and typing "nav_generate" and pressing enter, How long this will take is entirely up to how your computer is, But once it's done, shrek will chase you, if you don't want to do all that, then just go with the classic maps like construct and flatgrass.