Conditional step not working D365 Portal

Hi,

In a web form we have 3 steps , ST1 , ST2, ST3 .

After Step ST1 its optional to fill ST2 and After ST2 step ST3 will be shown up.

Requirement - I have to make ST2 mandatory .

So I open Step 2 and set - Type - condition

In Condition Tab - I set the condition new_quantity but its saying - "attribute not found"

ST1 is linked with entity E1

ST2 is linked with entity E2

I checked the schema name of field in Entity E2 it was correct

Can any one help me