When migrating from server to another , please make sure deploy these notes:

1-After migration successfully done , disable the service in the old server do not make it automatic to avoid running again the old server and conflicts can be occurred like (Mail server sometimes works and sometimes not).

2-Choose this path for the new system in the new server:

C: Manage Engine>Service desk plus

3-If the notification for requester and technicians stopped and you checked the notification rules and found everything is fine.please test the Notification System if not working.....check this issue with the concerned admin to check the firewall logs.