SQL – The EXECUTE permission was denied on Stored Procedure

The EXECUTE permission was denied on the object ‘STORED_PROC’, database ‘MYDB’, schema ‘dbo’

This massage is received when the SQL Server account under which you make the request doesn’t have permission to execute the stored procedure. you can overcome this problem by modifying the permissions of the SP.
If you want to grant public access, so all users can execute the procedure:

USE [DATABASE];
GRANT EXEC ON dbo.[MYSTOREDPROCEDURE] TO PUBLIC

If you want to tighten security to allow only specific users to execute the SP, which is advisable, then its:

USE [DATABASE];
GRANT EXEC ON dbo.[MYSTOREDPROCEDURE] TO MYUSER

OR

USE [DATABASE];
GRANT EXEC ON dbo.[MYSTOREDPROCEDURE] TO MYGROUP