I too have this issue of “loading messages. PLease wait” I have gone to the console as you instructed above,
There is an error listed the details for which are:
Uncaught SyntaxError: Unexpected token ‘;’
at new Function (<anonymous>)
at Function.v.template (underscore.min.js?ver=1.8.3:2)
at n.template (wp-util.min.js?ver=5.7.2:2)
at n.render (wp-backbone.min.js?ver=5.7.2:2)
at n.render (buddypress-messages.min.js?ver=8.0.0:1)
at n.setPreview (buddypress-messages.min.js?ver=8.0.0:1)
at p (backbone.min.js?ver=1.4.0:2)
at f (backbone.min.js?ver=1.4.0:2)
at c (backbone.min.js?ver=1.4.0:2)
at n.trigger (backbone.min.js?ver=1.4.0:2)