From fabric document create-join-channel, when I execute the command
peer channel create -o orderer.example.com:7050 -c $CHANNEL_NAME -f ./channel-artifacts/
Please make sure that channel name is new one and that there is no existing channel already with that name in the network.
for example, if you already created a channel with CHANNEL_NAME=mychannel, change the variable before you create another channel, by running something like export CHANNEL_NAME=mychannelanother