This error occurs when you see the terms & conditions page, click "accept" and are then left with a blank screen. Terms must be accepted on 1st August each year.
This error is usually an issue with cache.
If you clear your cache you should be able to then login if you refresh the page.
So if you are using google chrome > Click Ctrl+Shift+Delete > Clear Browsing Data > Advanced > Cookies & Other site data and Cached images & files selected > Clear data
Other information on clearing cache is available at: https://its.uiowa.edu/support/article/719