We are currently working on an issue where users may be redirected to an okta login page while trying to log into GeoNet. This login will not allow you to access to GeoNet with your Esri Account.
It appears that this issues is specific to the Internet Explorer (IE) browser and from mobile devices. To avoid this issue, sign into your Esri Account from the link at the top of the site prior to contributing within GeoNet.
"Sign In" at top of site will allow you to login correctly. - https://accounts.esri.com/?redirect_uri=https://community.esri.com/welcome