So I needed to use Cron to run a script on regular intervals. I quickly realized that running code without error messages was no fun & I needed to see what is going on.
There must have been a way to write it to a log but it seems like the way people usually handle error messages from Cron is via sending an email, so that's what I went for.
I followed this post & got it working
Getting my error messages emailed to me helped me find my mistake & now my script works.