Connection failed to broker! urgent

hi everybody
i have got a problem , i can't connect my dashboard to the broker server idk why , i didn't change anything and it was working fine
i'm getting this message in the node-red console : Connection failed to broker: mqtt://
i tried to make the connection using a js file , and this is the error :
Error: connection refused : server unavailable
so what do you think guys ? thank you in advance

Would suggest that the server refused your connection. Try to connect with an alternate MQTT tool to see if that works. Such as