GarageBand no guitar sound while I try to record, I can hear guitars in a headphones but no sound is recorded

Please help. I connect everything properly, I can hear my guitar and voice when I'm singing in my headphones. But only my voice is recorded but no guitar. I record through one microphone simultaneously both on one track. But it seams to select only my voice no guitar is heard after recorded. When I do the same on audacity it is working, so all ok, but when I go for GarageBand only my singing. How to solve it please?

Thank you