The app needs a browser released after early 2021. Yours is older, so it would only ever show a blank screen — which is what you were looking at, rather than anything being wrong with your account.
The quickest fix: open this page in Google Chrome. Chrome still works on older Macs and Windows PCs long after Safari stops updating. A phone or tablet will also work.
If you are on a Mac from around 2011 or earlier, Safari cannot be updated far enough on that machine, so Chrome is the way in.