Can you post a screenshot of your axis setup? So I can see what function/s your throttle axes are mapped to?
Also. Tests in other games are valid but DIView is a handy little software that you can use to check functionality.
You can find it here.
http://www.leobodnar.com/shop/index.php?main_page=page&id=12
(Bottom line, your throttle and PC are almost certainly fine but the function mapping in FS2020 is a bit…odd.)