I am just getting a smaller than usual sign in page, that constantly shows then goes off again, ?
Are you using a web browser or an email app and on what device are you using it?
If a web browser try clearing your web browser's history and cookies? When you do that make sure that you select the option "Clear All Time" if your browser offers that option.
You should also check that the zoom setting for the page size has not changed. You will find the setting to do that in the browsers settings or to change it press the CTRL and + or - buttons together to change make the page bigger or smaller.
I've been having this also.
I followed the advice in a post that said to try incognito browsing in Chrome. That worked.
BT just want me to reset my browser (when I loose all my settings and history).