When we try to create a related record from custom UI on Record Edit page, The rule base(New Record.xml) will not get executed and as a result the PRODUCT ID is not populating for a new record. Whereas the same will work on native UI. This is because of the New Record.xml is not calling when we create a related record.

Record ID will not assign for related record on Custom UI as below.



Record ID will Assign for related record on Native UI as below.

 This is a known issues on Custom UI pages,As the New Record.Xml file will not call when we access the Record Modify Screen on Custom Pages. As a workaround,We need to move the assign constraint to validation rulebase to assign Product ID for this use case as below. <constraint>         <name>AssignProdcutID</name>         <description>AssignProdcutID</description>         <usefor/>         <action>             <assign>                 <var>PRODUCTID</var>                  <op func="sequence">                     <const type="string">MQ_SEQUENCE_1</const>                 </op> </assign> </action> </constraint>