When it comes to PingTree campaigns, there is no functionality to directly reprocess a lead. The Ping Tree system works on a one time evaluation of all options to avoid sending again is it could result in accidental delivery in most cases.
If this is required as part of your process however, then you have a couple of options to aid you.
Export from the rejections and re-import
Simply run an export of your rejections and from the PingTree and reimport them.
From here a create new lead will be created and it will run through processing as well as re-evaluate and send to any matching destinations
Create a campaign that delivers into the PingTree
First thing to do is create a campaign that matches your delivery campaigns. This should have the same fields, validation rules and suppliers that the other campaigns on the PingTree share.
Once that is set up, if leads get rejected in this process, either through failed validation, required fields or even client rejections and caps, then they you can reprocess the lead that is on the main campaign before the ping tree.
Reprocessing here, it will essentially create a new lead which will be delivered into the PingTree.
What about the original lead?
It's worth noting, that in both of these methods, your original rejected lead stays on the system as a rejection.