we've had phpMyFAQ installed for quite some time now. We only just recently realized that the built-in search engine doesn't work perfectly. i. e. we noticed that for each picture we upload, it will create a coded base64 string for that picture in the article-page source. It just happens to be that if you search for short items (about 3 characters long) you will surely find a lot of articles that don't have the keyword in it, it just appears to be in the aforementioned base64 string.
Now we wanted to switch to elasticsearch. I added the elastic.co repo to my debian apt and installed the package. After a bit of configuration (changed hostname the logging paths) i tried the search field on the phpMyFAQ page and I got this error:

The documentation doesn't tell me anything why this error occurs, nor how to index the sql database of my site. Still, the elasticsearch server is running as you can see here

I just can't get it to work with phpMyFAQ
Any ideas?