Flexischools have recently done some updates to their site which has affected some people's interaction with the site. Flexischools have suggested that you clear the cookies , by clicking on the padlock at the very left of address the bar, followed by the cookies button in the dropdown box.  After this, click the remove button until all the cookies have been removed. Finally refresh your browser and try logging in again. 

If your having issues with the APP, uninstall and then reinstall and then try again