How do I get database rows from a custom table using wpdb?

I’m trying to get particular rows from custom table into an object using wpdb.

From the cli of the mysql client, this line yields the rows I want:

select * from wp_94b3c05783_wpforms_entries WHERE entry_id IN ( 738,  552, 551   )

This is my translation of that instruction into a wpdb call:

$results = $wpdb->get_results( "SELECT * FROM  {$wpdb->prefix}wpforms_entries WHERE ID IN( 738, 552, 551  )"  );

Inspecting $results using ‘var_dump’ returns an empty array.

So, the mysql query works – but when I wrap it in a wpdb call I get nothing back.

I’m definitely testing the queries against the same database as the WordPress instance is using.