@AlwinJebakY 

is it working fine with admins? -> if yes then it's some ACL issue

Try creating query_range ACL on both the fields and add proper role

Also user should have read access to fields used in that attribue

check this KB

Service Catalog — Autocomplete Not Working with Custom Fields in ref_ac_columns Using AJAXTableCompl...

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@Ankur Bawiskar  

I tried all this ways, but now also I'm not getting any values on that field?
Did you know any other ways ?

@AlwinJebakY 

is it working fine with admins with that attribute ref_ac_columns_search?

@Ankur Bawiskar 
It is working previously for same user, now only got an error and I checked with another users with same access level they can able to see the records.

@AlwinJebakY 

if it's working with admin and some non-admin and not working for some other non-admin then it's access issue