Please help

I installed Netxms 4.1.420 on Linux Ubuntu 20.04 LTS.
I installed everything according to the documentation (netxms admin guide), database, netxms server, mariadb.ddr, netxms agent, etc.
Configuration:

1. Linux ubuntu (Server: IP - 192.168.x.x - local network)
2. etc/nxagentd.conf

• LogFile=/var/log/nxagentd
  -MasterServers=192.168.x.x (instead of 127.0.0.1)

3. etc/netxmsd.conf

• DBDriver=mariadb.ddr
• DBServer=localhost
• DBName=netxms_db
• DBLogin=netxms

4. Desktop Management Console installed
5. Web Management Console installed

When I log into the system, the ip address of Linux Ubuntu (agent) is 127.0.0.1. I manually enter the IP address 192.168.x.x, perform pooling (Poll - Status, Configuration, etc.) everything is fine for a few minutes. The IP address 127.0.0.1 is automatically returned again. and there is no communication (Cannot connect to netxms agent - connect failed and internal error).

Where did I go wrong, do I need to check something else??

Thanks, best regards.