Refresh can be done through tapping '3 dot' button on top right inside a list. On Mac, you can CMD-R or click icon on bottom left pane.
If you're using iOS 12, things can vary and it's a bit complicated. If you haven't upgraded iOS Reminders database on iOS 13 and Catalina, it will still sync. You may check related info on below posts.
https://forum.goodtaskapp.com/t/things-to-know-about-ios-13-and-macos-catalina
Thanks!