Shell script with executable permissions returns "command not found"

Roy Hinkley asked:

I have a shell script file with executable permissions:

-rwxr-xr-x   1 root   root       1147 Jan 26  2017 my_script

Even running it as root – fully qualified (path/to/file/my_script) I get the following error:

-bash: my_script: command not found

SELinux is being enforced and the context label is:

unconfined_u:object_r:var_t:s0

But even attempting to execute with SELinux disabled

Current mode:                   permissive

does not remedy the error. This script has executed as expected in the past.

What am I not understanding – why is this exception being encountered?

Reference:
CentOS release 6.9

./my_script