A beta version is an early, not yet fully developed version of a new website; a preview, so to speak. This means that the page is already functional and usable, but does not yet correspond to the final version and also does not yet contain all content. However, the beta version does give you an early insight into the most important innovations which will be soon replacing the current SBB.ch website.
It is therefore to be expected that not all functions will work perfectly in the beta version, and that it will not be entirely accessible for all users.