Sometimes Path Hints won't be shown if:
- The URL does not contain the
templatehintsparameter. - Developer Client Restrictions has an IP addressed listed that isn't yours.
- The cache was not flushed after changing the option.
- The site was changed to Production mode.
Developer Client Restrictions can be check in Stores -> Settings -> Configuration then Advanced -> Developer -> Developer Client Restrictions. Check that the Allowed IPs field is either blank, or contains your IP address.