According to https://github.com/gnembon/fabric-carpet/wiki/How-to-spawn-proof-with-auto_light.sc

The following line needs to be changed
&& air(lpos) && light(lpos) < 8 && sky_light(lpos) < 8

But that line does not exist, however, in line 14 in the recent script, this line should control it:
global_light_ground = true; //Whether or not we want to light the surface
But no matter what, I can't get this to work.

This seems to be an issue with the new version of the script, reported in gnembon/scarpet#317.

As a workaround, you can get the older version and apply the instructions on the wiki page.

Here's a link to the older version: https://github.com/gnembon/scarpet/raw/fe150339ab32283acac0b63e43fcfd63d8f31467/programs/survival/auto_lighter.sc

This seems to be an issue with the new version of the script, reported in gnembon/scarpet#317.

As a workaround, you can get the older version and apply the instructions on the wiki page.

Here's a link to the older version: https://github.com/gnembon/scarpet/raw/fe150339ab32283acac0b63e43fcfd63d8f31467/programs/survival/auto_lighter.sc

Thanks for the reply, it worked.

Closing this as a dupe of the issue on the scarpet repo.