unable to retrieve article via SOAP OXERPGetArticles

Hello,

SOAP methods oxerpGetArticles and oxerpGetArticle keep returning empty results and I don't know why. Other methods seem to work fine, e.g. oxerpGetOrders returns all orders without problem.
The issue appeared when we moved to different OXID webshop. The configuration may be slightly different from the previous one.
Is there a way to debug a SOAP method call in OXID?
What conditions must be met for an article to be retrievable by SOAP?

Best regards,
Kgc