Permission Denied on INSERT

Howdy,

We're getting a permission denied error on an INSERT and cannot figure out why:

[postgres@thiludbapql01 log]$ psql -U treg csbtest
Password for user treg:
psql (16.6)
Type "help" for help.

csbtest=# show search_path;
        search_path
----------------------------
 csbtfsprd, interface, treg
(1 row)

csbtest=# grant usage on schema treg to treg;
GRANT
csbtest=# GRANT SELECT, INSERT, UPDATE, DELETE ON ALL TABLES IN SCHEMA treg TO treg;
GRANT
csbtest=# GRANT USAGE, SELECT ON ALL SEQUENCES IN SCHEMA treg TO treg;
GRANT
csbtest=# GRANT EXECUTE ON ALL FUNCTIONS IN SCHEMA treg TO treg;
GRANT
csbtest=# insert into treg.cd_combined_office_mappings (combined_office_id, tcsi_office_id, sb2_account_id, account_name, city, postal_code, state, category, is_preferred, is_closed, is_parent)
csbtest-# values (('734309'::int8),('S.668863.785512'),('668863'::int4),('Testing Something'),('Beaverton'),('97008'),('OR'),('Carrier'),('Y'),('N'),('Y'));
ERROR:  permission denied for schema treg
LINE 1: SELECT 1 FROM ONLY "treg"."cd_combined_offices" x WHERE "com...
                           ^
QUERY:  SELECT 1 FROM ONLY "treg"."cd_combined_offices" x WHERE "combined_office_id" OPERATOR(pg_catalog.=) $1 FOR KEY SHARE OF x
csbtest=#

Any help would be greatly appreciated, please.

Thank you,

Sam