If running scripts within /etc/cron.* directories, make sure your scripts:
- are executable,
- match the Ubuntu/Debian cron script namespace
(^[a-zA-Z0-9_-]+$).
So for example if you've script with extension (such as .sh) won't work.
To print the names of the scripts which would be run on hourly basis, try:
sudo run-parts --report --test /etc/cron.hourly