I'm a sucker for this sort of thing build into a product, so I was stoked to see it appear. The 'let the celebrations begin' doesn't load - it does a mini-refresh of the page, and nothing changes. This is on the desktop version.
The mobile version also has the 'offer' available. The mobile app button works, but I don't think as intended. It launches a browser in app, and loads the desktop in mobile version (as if you are logging in via Safari or equivalent), asking me to log in from scratch. Once you log in, you are now in the desktop mobile version, again presented with the button. Clicking the button here functions just like the desktop version, performing a mini-fresh.
I've tried across different devices/browsers without any luck.
As a side tip, I recommend an email about the birthday reward, as I wouldn't have noticed without opening the app/desktop.