Regarding PDI issue

[Gajendra singh]

Developer Instance is undergoing unscheduled maintenance. Get Notified when your PDI is available.

[svirkar420]

Hi @Gajendra singh , Though its not clear what you want to say, but if PDI is going into unscheduled maintenance or in a sudden maintenance then this is not an issue you need to worry about, this has happened a lot with me. 
Just try to refresh the PDI from "https://developer.servicenow.com/dev.do" page 1-2 times and then wait for some time and then log in again, this will help you retrieve your PDI.

If this solution helped you Please Mark this solution as accepted and helpful as it will be helpful for other users as well.
Best Regards.
Saurabh V.

[Nikhil Bajaj9]

Hi @Gajendra singh ,

If PDI is going in maintenance, no one can tell you when it will be back. Once Maintenance is completed, you will get an email that maintenance completed. Check your PDI at this time. Unfortunately there is no support available on PDI.