No Laserscan received for many seconds for navigation ?

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Hi Guys,

I m trying to set up the 2D Navigation Stack. Everything works fine beside of the integration of the laser_scanner. I set up all the transformations as well as publishing all the needed data as map, odom and laser_scan for autonomous navigation. Nevertheless amcl is always saying this:

[ WARN] [1488657566.744750961]: No laser scan received (and thus no pose updates have been published) for 1488657566.744665 seconds. Verify that data is being published on the /scan topic.

I have been working with ROS now over 2 years and i dont understand this mistake. My tf_tree (map->odom->base_link->laser_scanner) doesnt show any errors as well as all published topics show the status ok in rviz. If I m using the fake_amcl node everything works fine. Does anyone know what I can do ? The advice that i found here, to set the sim_time to true causes that amcl isnt loading the map.

Thanks for help :)