phpthumbof not working in ArticleRowTPL

Hi everyone,
I actually have the problem that phpthumbof doesn't create a thumbnail (it does nothing) of my image-tv at the articleRowTpl (the listing of all articles). I have process TVs on (The TV itself is working fine). Have I missed to setup something?

I'm using it like in other templates (for example for getResources):

[[+tv.news-teaser-image:phpthumbof=`w=253&h=245`]]


Modx Revo 2.3.1
Articles 1.7.8
PhpThumbOf 1.4.0

Thanks in advance!