Hello, So the issue is as stated above. I am trying to run autonomous navigation on a simulated environment in gazebo using ROS Noetic, I've created the map using Gmapping node and when I try to localize the robot using AMCL it doesn't work.

Here's the launch file

<!-- Arguments -->

<arg name="map_file" default="$(find diff_navigation)/maps/new_map.yaml" />

<arg name="initial_pose_x" default="0.0"/>
<arg name="initial_pose_y" default="0.0"/>
<arg name="initial_pose_a" default="0.0"/>

<!-- Map -->
<node name="maps" pkg="map_server" type="map_server" args="$(arg map_file)"/>

<!-- AMCL -->
<node pkg="amcl" type="amcl" name="amcl" output="screen">

  <param name="min_particles"             value="500"/>
  <param name="max_particles"             value="3000"/>
  <param name="kld_err"                   value="0.02"/>

  <param name="initial_pose_x"            value="$(arg initial_pose_x)"/>
  <param name="initial_pose_y"            value="$(arg initial_pose_y)"/>
  <param name="initial_pose_a"            value="$(arg initial_pose_a)"/>
  <param name="gui_publish_rate"          value="50.0"/>

  <remap from="scan"                      to="$(arg scan_topic)"/>
  <param name="tf_broadcast"              value="true"/>

  <param name="odom_model_type"           value="diff"/>
  <param name="odom_frame_id"             value="$(arg odom_frame"/>
  <param name="base_frame_id"             value="$(arg base_frame)"/>
  <rosparam command='load' file="$(find diff_navigation)/params/amcl_params.yaml" />
</node>

Attached below are the outputs of usual debugging procedures :

1. rostopic list

   amcl/parameterdescriptions /amcl/parameterupdates /amclpose /clickedpoint /clock /cmdvel diagnostics /diffrobot/laser/scan

   /displayrobotstate /gazebo/linkstates /gazebo/modelstates /gazebo/parameterdescriptions /gazebo/parameterupdates /gazebo/performancemetrics /gazebo/setlinkstate /gazebo/setmodelstate /initialpose /jointstates /map /mapmetadata /mapupdates /movebasesimple/goal /odom /particlecloud /rosout /rosoutagg /tf /tfstatic

2. rosnode info /amcl

Node [/amcl]
Publications: 
 * /amcl/parameter_descriptions [dynamic_reconfigure/ConfigDescription]
 * /amcl/parameter_updates [dynamic_reconfigure/Config]
 * /amcl_pose [geometry_msgs/PoseWithCovarianceStamped]
 * /diagnostics [diagnostic_msgs/DiagnosticArray]
 * /particlecloud [geometry_msgs/PoseArray]
 * /rosout [rosgraph_msgs/Log]
 * /tf [tf2_msgs/TFMessage]

Subscriptions: 
 * /clock [rosgraph_msgs/Clock]
 * /diff_robot/laser/scan [sensor_msgs/LaserScan]
 * /initialpose [geometry_msgs/PoseWithCovarianceStamped]
 * /map [nav_msgs/OccupancyGrid]
 * /tf [tf2_msgs/TFMessage]
 * /tf_static [tf2_msgs/TFMessage]

Services: 
 * /amcl/get_loggers
 * /amcl/set_logger_level
 * /amcl/set_parameters
 * /global_localization
 * /request_nomotion_update
 * /set_map


contacting node http://abdul-Nitro-5:45419/ ...
Pid: 64109
Connections:
 * topic: /rosout
    * to: /rosout
    * direction: outbound (42243 - 127.0.0.1:39362) [20]
    * transport: TCPROS
 * topic: /tf
    * to: /amcl
    * direction: outbound
    * transport: INTRAPROCESS
 * topic: /tf
    * to: /rviz_visualize
    * direction: outbound (42243 - 127.0.0.1:39364) [13]
    * transport: TCPROS
 * topic: /clock
    * to: /gazebo (http://abdul-Nitro-5:42765/)
    * direction: inbound (60380 - abdul-Nitro-5:56989) [15]
    * transport: TCPROS
 * topic: /tf
    * to: /amcl (http://abdul-Nitro-5:45419/)
    * direction: inbound
    * transport: INTRAPROCESS
 * topic: /tf
    * to: /robot_state_publisher (http://abdul-Nitro-5:37439/)
    * direction: inbound (48362 - abdul-Nitro-5:59369) [18]
    * transport: TCPROS
 * topic: /tf
    * to: /gazebo (http://abdul-Nitro-5:42765/)
    * direction: inbound (60402 - abdul-Nitro-5:56989) [21]
    * transport: TCPROS
 * topic: /tf_static
    * to: /robot_state_publisher (http://abdul-Nitro-5:37439/)
    * direction: inbound (48364 - abdul-Nitro-5:59369) [19]
    * transport: TCPROS
 * topic: /diff_robot/laser/scan
    * to: /gazebo (http://abdul-Nitro-5:42765/)
    * direction: inbound (60396 - abdul-Nitro-5:56989) [23]
    * transport: TCPROS
 * topic: /initialpose
    * to: /rviz_visualize (http://abdul-Nitro-5:39879/)
    * direction: inbound (46142 - abdul-Nitro-5:36229) [14]
    * transport: TCPROS
 * topic: /map
    * to: /map_server (http://abdul-Nitro-5:42407/)
    * direction: inbound (43698 - abdul-Nitro-5:45827) [16]
    * transport: TCPROS
 * topic: /map
    * to: /maps (http://abdul-Nitro-5:34731/)
    * direction: inbound (57116 - abdul-Nitro-5:45413) [17]
    * transport: TCPROS

Link to tf tree As you can see map is not being published !

Also I checked the frame id's of /map , /odom, /diff_robot/laser/scan to verify that the frame id's match the ones used by amcl. I will be at your disposal for any further details. thanks and regards.