Can't sign in -why do you say my password is incorrect-I haven't changed it?

I have tried eight times to sign in to my Firefox account an set up thunderbird on my new tablet but every time it refuses to let me sign in and says incorrect password - its the same password I have used for years on all my other devices - you have sent 6 email codes telling me to input in order to sign in and none of them work - I just keep getting 'incorrect password flash up' .Before I go completely mad , can you please just check the system and let me sign in as normal?