IP address conflicts not work ( install IPAM only not used UDT)

Kindly check first the document below.  Look for IP Address conflicts.

https://documentation.solarwinds.com/en/success_center/ipam/content/ipam-ip-address-conflicts.htm

Once you understand the scenarios, you will be able to identify if your IPAM is indeed getting all the information it needs to alert for IP Address conflict.

I test Static and Static used scan SNMP to 2 PC and scan SNMP neighbor. 2 PC ping time out and ping reply alternate between 2 machines. show arp on switch see MAC address alternate between 2 machines. but IPAM does not detect IP Conflict. 

event on IPAM see change MAC address not detect IP Conflict

On what you are describing, the ARP table simply switches MAC address and does not really show both value at the same time, is that correct?

Same time, but sometimes IPAM sees a mac change, sometimes you don't see it.

that means the polling is not being able to catch the MAC address change.  When the polling happens, the arp table should catch both of them having the same IP.

What happens when you actually check the IP Address Details?  It is only listing one MAC?  did you check the MAC address History of the said IP?  Is it showing both MAC address?

At one point in time, the switch saves the only MAC address that replies.

I test 2 Orion ipam+udt show ip conflict but ipam only not show ip conflict. 

Both server settings are the same.

IPAM only

IPAM + UDT

Ok.  It seems what you are looking at is SNMP neighbor vs. SNMP neighbor.  That is actually not listed on the IP Address conflict scenario.  My take here is that the IPs are getting conflicts but since you are only getting it from one source which is SNMP neighbor, it is not being detected.  You might want to send this over to support for further verification.