iMessage won’t sign in on Mac mini

Everything apple related works perfectly including FaceTime, I have complete access to all my account information and services except iMessage, this isn’t a big deal however it is a gimmick I would like to resolve, I have tried my iCloud to log into my iMessage and I am greeted with “unable to authenticate” or sometimes “ wrong password or username”, it Varys depending what I change, I have tried my daughters iCloud information and it goes right to verification, which is what my account will not do!, I am completely new to the Mac scene and this is my first ever apple computer so go easy on me I don’t know what I’m doing!