bash: ./ipsweep.sh: cannot execute: required file not found

Im trying to run an ipsweep script i wrote following a video and i found a common problem being bash: ./ipsweep.sh: cannot execute: required file not found , i have given permissions to read, write and execute using chmod u+x ipsweep.sh any insight would be helpful.

here is the script –

#!bin/bash

if [ "$1" == "" ] 
then 
echo "You for got to put in an IP!"
echo "Syntax: ./ipsweep.sh 192.168.4" 

else
for ip in `seq 1 254`; do
ping -c 1 $1.$ip | grep "64 bytes" | cut -d " " -f 4 | tr -d ":" &
done
fi