I have had issues with SQL Server connector whenever I make changes within the tables or even change my password.
The first thing I would try is recreating the stored procedure with a new name and everything (basically copy paste the stored procedure into new one with new name), then deleting the current flow step and replacing it with a new one to the new stored procedure.
If that doesn't work I would recreate the flow fresh, and/or go into my Data>Connections and deleting the current SQL Server connection and making a new one. Then delete and remake the SQL Server connection steps in the flow with the new connector.
Seems like a lot of work, but I know PA connectors to SQL Server doesn't always work seamlessly.