Postgresql rds: relation .... does not exists

This seems to be a question that is asked alot all of the answers that I have read do not seem to pertain to this situation. I maybe wrong, I am a newbie but here is the question.

I am using psql 11 in amazon rds. I have one db on the instance with 2 schemas. It is running slow in testing so I was going to run the missing index query.

SELECT
    relname,
    seq_scan - idx_scan AS too_much_seq,
    CASE 
        WHEN seq_scan - coalesce(idx_scan, 0) > 0
          THEN 'Missing Index?'
        ELSE 'OK'
      END,
    pg_relation_size(relname::regclass) AS rel_size,
    seq_scan,
    idx_scan
  FROM  pg_stat_all_tables
  WHERE
    schemaname IN('schemaname') AND
    pg_relation_size(relname::regclass) > 80000
  ORDER BY too_much_seq DESC;

When I run it in this new environment I am getting a relation does not exists.

I have checked permissions, ownership, lowercase, I can see the table, run queries against the table, however I can't seem to get this query to work. If I do a SELECT * from pg_stat_all_tables I can see all of the tables that do not exists in he other query.

I am not sure what is wrong. I am pretty sure it is in the pg_relation_size(relname::regclass) section, I think that is where it is not finding the relation, however I have been unable to find documentation on this function that would appear to shed light on my issue.

Any assistance would be appreciated.