Beta Client won't let me adjust masteries

I was queuing up for a ranked game with and wanted to make sure that my masteries were correct. While on that page I was unable to create or edit any mastery pages. Upon switching to the legacy client i suddenly had 5 empty mastery pages and had deleted 2 that i regularly use.

Doesn't seem to be an issue on the legacy client, but definitely happened on beta client.

Running windows 10 with all updates applicable