We talked earlier and you said that the device is setup to use SNMP version 3 to send the traps.
To get the XI server to accept SNMPv3 traps, the /etc/snmp/snmptrapd.conf file has to be updated with the username, credentials, etc and this KB article has the various settings that need to be done.
https://support.nagios.com/kb/article/nagios-xi-snmp-trap-v3-configuration-827.htmlWhat you are going to need is the username, encryption password, the encryption protocol, the privacy password, the privacy protocol and the EngineID from the device if needed if the device uses an EngineID.
You will have to go the manufacturer of the device to see if it uses an EngineID and how to get that.
The first time a trap is received by the Nagios XI server, it has to be configured.
If you login to the XI GUI and go to the Admin > Unconfigured Objects menu, and you see that Trap there from the switch, you will have to configure it and from then on, the system will automatically receive it.
Here are some other articles you can review for more details on SNMP Traps and Nagios XI.
https://support.nagios.com/kb/article/nagios-xi-manage-mibs-architecture-73.htmlhttps://support.nagios.com/kb/article/nagios-xi-snmp-trap-tutorial-77.htmlhttps://support.nagios.com/kb/article/snmp-trap-snmptt-service-89.htmlThank you.