HermannG on "zp_OpenStreetMap: Blank space"

I tried a lot to get zp_OSM working following the instructions on github. Unfortunately, I did not have success for 2 weeks. I tried several themes (especially basic and libratus), put the printOpenStreetMap() in image.php (hopefully in the right place).
There is obviously some space reserved below the picture, but no map displayed (only blank background).

I could not find any errors in the logs, so I ask here for advice, maybe someone has a suitable "image.php" I can try with.

Thanks for any help
Hermann