Yahoo mail won't stay at the newest style and keep bounce back to the very old style

[Happy Hopping]

So I have been using the old style yahoo mail for the longest time, and recently click Switch to the Newest yahoo mail as my font on the old mail is too small and I can't find a way to change it

but after I switch to it, the next time I turn on my PC, that website bounce me back to the old style. And it has happened a few times already. Is there a way to fix this