If you see the following issue after upgrading to SQL 2019
"Internal error: An expression services limit has been reached. Please look for potentially complex expressions in your query, and try to simplify them."
Set the database to SQL 2017 compatibility mode
ALTER DATABASE [TheOrderExchange] SET COMPATIBILITY_LEVEL = 140
Check the stored procedure runs, then try set it back to 2019 compatibility mode
ALTER DATABASE [TheOrderExchange] SET COMPATIBILITY_LEVEL = 150