Follow the below procedure.....
Step 1: Primary server i run below queries.
Note: here MyDB is your database name.
1)delete from msdb.dbo.log_shipping_primaries where primary_database_name = 'MyDB'
2)delete from msdb.dbo.log_shipping_monitor_primary where primary_database= 'MyDB'
3)delete from msdb.dbo.log_shipping_primary_databases where primary_database= 'MyDB'
4)delete from msdb.dbo.log_shipping_primary_secondaries where secondary_database= 'MyDB'
Step 2: Secondary server i run below queries.
1)delete from msdb.dbo.log_shipping_secondary where primary_database='MyDB';
2)delete from msdb.dbo.log_shipping_monitor_secondary where primary_database='MyDB';
3)delete from msdb.dbo.log_shipping_secondary_databases where secondary_database='MyDB';
Regards
Chowdary...