user lib function not found

user lib function not found

I'm trying dll into blitz3d.
I receive the following error message "user lib function not found".
The dll source code is write in blitzmax.
I think that the problem is due of a bad type blitzmax String conversion into B3dn, but i'm not sure.
Can you help me to found the solution of my problem , please ?

I'have a test case where you can found on the following link :

http://hedgehog.team.free.fr/folder_public/TestCaseDll.zip

Thanks