I spent more time to be even more complete... here goes..
If no items are replicating, it probably is a permissions issue
please reread the requirements to configure the service account.
if you are on Exchange 2007 or Exchange 2010, be sure to do this:
Items not replicating
If just some items are not replicating, there may be other things going on which are data related or relationship configuration options.
If this is an upgrade from a very old version of Add2Exchange, those older versions did not employ SQL transaction processing. Rebooting the server in the middle of a sync could potentially put the system in an unstable state. This tip will evaluate and remove those rows which are stopping proper replication. Once this is done and the Add2Exchange installation is updated to the latest release, this will never happen again.
Stop a2e from Service Control Manager utility
do sanitize db: http://support.diditbetter.com/kb/A2E_183.aspx
Another situation: If it is an appointment on a source Calendar not replicating, it is possible the replication interval within the relationship is not set wide enough to cover the start date of the item. Sometimes it is in the past and sometimes it is prior setting or sometimes it is the post
Another situation: If the items which are not replicating are recurring Calendar items or if it is a birthday, then see this tip: http://guides.diditbetter.com/a2e-guide/recurring_appointments.htm
Another situation: If no items are replicated to a specific user, it is possible that when making the relationship the setting to copy no existing items is selected. This means that no existing items in the source will be replicated to the destination, only new items made directly in the source. the solution here is to delete the relationship and select to remove the destination items, close the A2E Console and let it desync whatever got copied, and then remake the relationship and select to copy all items.
Another situation: If some items are not being copied from a private folder, it is possible that within the relationship you have selected not to copy private items
If you want to copy private items, uncheck this. If you do not use private items, it could still be left checked, and the user has the ability not to copy personal items around, which can be handy.
Another situation: If there are all or a few Contact items not syncing, it is possible that this source folder is also a destination of another relationship. If so, Add2Exchange does not copy a copy, so you may need to make another relationship or two from the original source to the destination folder. We call this a full mesh relationship, or folder grouping, where anything anywhere gets copied. http://guides.diditbetter.com/a2e-guide/folder_grouping.htm
Another situation: Sometimes users have left copies of items in the source folder which came to that folder as the destination copies from another relationship. since Add2Exchange will not copy a copy, and ONLY if this folder is not the current destination of another relationship, you could clean the copy tag off of the items in place.
To clean the copy tag off of the items IF and only IF this is not the destination of another relationship, you can surgically remove the tag with the Inspector and Surgeon General
License the toolbox
Go to Inspector General
Pick the source folder
Go to the Surgeon General
Unlock the named properties
Let it finish evaluating all the items
move the cursor to the right
see the column a2e copy
if there are green copies there, then you have copies from another relationship.
You can select remove A2ECopy=T and select Remove NP
it will make the copies as originals. Be careful on this one, you may want to get some help: