After logging in, I see a message "Request Deferred" - what does that mean?

"Request Deferred" simply indicates that your app will check again in a few minutes to sync all data from the server. During high server load at very large events, the apps automatically adjust their timing when they sync across other devices. There is nothing wrong and you can keep using the app normally. Synching and data backups will happen in the background the next time possible.