[Why Cant They Cant Hear Me?]

Good Afternoon All, 

I am new to GMRS, got some amazon special radios (Baofeng GM-15PRO) and have been playing around hitting the local repeater and talking with my wife as I test and learn all of this. I live in the Madison WI area and can hit the Baraboo repeater which is about 21ish miles north. I went up to norther WI last weekend and could talk to her my wife at home and i was 40ish miles north of the repeater no problem.     Sunday night at home some chatter came over the repeater, someone from Central Illinois and Milwaukee Wis. were talking. I could hear them clearly, but when I reached out no response to me at all.    What am I doing wrong? What do i need to change/adjust for them to hear me?