Extended search with custom taxonomies and wpdm

Hello,
in my project I want to search for custom post types from wpdm (WordPress Download Manager).
There are wpdmcategory, produkte and gebinde custom taxonomies that are create with the following code:
taxonomies

The searchform.php contains this code:
searchform.php

The query gets build with this script:
Building query args

With an url like this:
s=searchstr&post_type=wpdmpro&pc=fr&wc=logos&gc=03l

$searchQuery is the following:

Array(
    [s] => searchstr
    [post_type] => wpdmpro
    [tax_query] => Array
        (
            [relation] => AND
            [0] => Array
                (
                    [taxonomy] => produkte
                    [field] => slug
                    [terms] => fr
                )
            [1] => Array
                (
                    [taxonomy] => wpdmcategory
                    [field] => slug
                    [terms] => logos
                )
            [2] => Array
                (
                    [taxonomy] => gebinde
                    [field] => slug
                    [terms] => 03l
                )
        )
)

But it isnt working.
What is wrong with my query?
I want to find posts that are in all the taxonomies selected in the form and contain the search string.
If no taxanomy is selected it should only find posts that contain the searchstring.
Can you help me please?