Creating executable from shell script

I'm creating an executable from shell script, say upload_data.sh. It basically uploads data into an interface table. The shell script is in the bin folder with many other scripts used successfuly as executables for various concurrent programs in the system.

I then ran the command

ln -s $FND_TOP/$APPLBIN/fndcpesr $CUSTOM_TOP/bin/upload_data

It created the link and I can see it in the ls -la command. However, when I run the concurrent program, I'm getting the error "FND-CP-ESP: Child: exec:: No such file or directory".

In trying many different options and looking into other executables in our system, I created an upload_data file (without the .sh) with the following information and that seems to work. I need clarification on what needs to be done to create an executable from a shell script and why the above link command is not working as documented in our environment.