can't select class

Hello! I used to play on the server quite a while back (like, 2017...) and logged back on to play again but I'm unable to select a class on the class selection screen. For reference I'm playing on a Mac w/ a trackpad (I've got no mouse on hand right now...) I've tried right clicking, left clicking, holding down the click, etc. I'm not sure if anything can be done or if I do need to have a mouse on hand to play. If so no prob!

 

You should be able to use the right mouse button to change your class. Have you made sure that the input you use to right click is bound to "Use Item/Place Block" in the minecraft settings?