Error inserting data into users_data table

Problem/Motivation

We have an okta integration for authentication on our Drupal site (dev & live instances) which was working for all our users that were onboarded in the first phase of the project. However, in the past 2 months we now see that the SAML authentication is failing and new users that are onboarded are no longer being created in Drupal, which was working previously. Instead, now it just throws an error back with the phrase "Error encountered while processing SAML authentication response; details have been logged." The drupal site shows us an error come up, but our Okta system shows that the authentication was successful.

We also see from the Drupal logs an error that it is unable to create the users as the drupal user id is null.

Any help on what could of caused this issue is highly appreciated as we are currently completely blocked from onboarding any users via our standard process.

Steps to reproduce

See below the error message we're seeing:

No matching local users found for unique SAML ID.

Drupal\Core\Entity\EntityStorageException encountered while processing SAML authentication response: SQLSTATEconstraint violation:1048 Column 'uid' cannot be null: INSERT INTO "users_data" ("uid", "module","name", "value", "serialized") VALUES (:dbinsert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4); Array ( [:db_insert_placeholder_0] => [:db_insert_placeholder_1] => tac_lite [:db_insert_placeholder_2] => tac_lite_scheme_1 [:db_insert_placeholder_3] => a:1:{s:9:"companies";a:1:{i:12;s:2:"12";}} [:db_insert_placeholder_4] => 1 ) in _Drupal\Core\Entity\Sql\SqlContentEntityStorage->save() (line 810 of /code/web/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php).

Proposed resolution