LookML error "Can't construct persistent derived table"

[simonlee9449]

I created datagroup and persistent derived table as below. but it keeps giving me an error. 

model
```

connection: "chai_redshift_production"

include: "views/**/*.view.lkml"

datagroup: hourly_datagroup {
  max_cache_age: "2 hours"
  sql_trigger: "SELECT EXTRACT(HOUR FROM NOW())" ;;
  description: "cache data for max 2 hours and refersh it every 1 hour"
}
```

view
```

# If necessary, uncomment the line below to include explore_source.
include: "/V1/production/card/redshift/production_card_redshift.model.lkml"

view: prejoined_payment_pdt {
  derived_table: {
    datagroup_trigger: hourly_datagroup
    distribution_style: all
    explore_source: prejoined_payment {

...

```

error msg
```

There are serious errors with this LookML code that could prevent queries from running.

Can't construct persistent derived table prejoined_payment_pdt, connection chai_redshift_production could not be registered

prejoined_payment_pdt.view:5 production_card_redshift:prejoined_payment_pdt

```