I Think Why This Might Be Happening Might Be Because Of A Flash Related Issue In The Browsers' System..

Now, I Don't Know If The Browsers' That Were Affected Have Anything To Do With Flash Ending Support At The End Of This Year

But Still, There Still Must Be A Possibility As To Why All Of A Sudden Users' Are Unable To Sign In To Play The Game As Intended As To A Reason Why That Is The Case