We don’t have crystal balls here on the forum… so if you need any further help you will have to provide as much details as possible about your situation (be exact), e.g. about your hardware, the exact name and version of your board, exact version of libraries used (add URL’s of their source), what IDE are you using? Have you selected the correct board, what pin mappings have you configured. Is there a gateway nearby, do you have your own gateway (LoRaWAN compliant 8 channel)?
Have you already tested your board with a basic sketch (not LoRaWAN) e.g. blink example. Are you able to output a simple string to the serial port? What do you see in the TTN console application/end device/gateway traffic? What is your region and do you have correctly configured this in the software? What TTN (Console) version are you using, TTN V2 or the new TTN V3, etc.
Double check the keys you have entered (byte order is important). Any typo will make it fail.
What have you already tried and what did exactly happen?
See How do I format my forum post? for tips about how to post code and text logs.