Hi folks
https://www.phplist.org/manual/books/phplist-manual/page/api-and-integrations
On the “Enable the API” step, we have a third sub-step:
Delete this folder entirely: public_html/lists/base/var/cache
Both me and my employer, individually read this as delete the folder.
And then spent the full day wondering why nothing worked which was made double fun because the error logging wasn’t working.
It wasn’t until I tried it on my own server, that I realised deleting the entire folder caused permissions issues.
As such, instead I think it would be better if the above statement was:
Delete all the files inside this folder: public_html/lists/base/var/cache
This should stop people like myself who are easily confused. 
Regards,
JJ