The problem with approving a Claim from Mtree is that the Mtree claims process won't add the vital info that PP now needs, which is added during the the initial Add Listing Process from the Front End and the Payments Process.  This information is a guide one what you will need to do to make the Mtree Claims process work with mtree.

Firstly lets look at the Standard Claims process in Mtree:
1. Admin creates a listing in Mtree Backend.
The listing is owned by Admin (thus making it clamable)

2. User Claims the Listing.

3. Admin receives email advising a claim is being made.

4. Admin Approves the listing,
This changes the owner from Admin to the Users Username/ID. Email is sent to user advising the claim is complete.

Working with Mtree Claims and PaymentsPlus adds a couple of processes for both Admin and the User.
Mtree with PaymentsPlus the process is like this (Note I've added some coments here for some things you should change):

1. Admin creates a listing in Mtree Backend.
The listing is owned by Admin (thus making it clamable)

2. User Claims the Listing.
As Admin you should alter the texts in the Mtree Language file to explain the new processes to the user. You could also modify the Claims form if you wanted again to make the process clearer.  The Claims form is page_claim.tpl.php ou will need to point out to the user that the listing will not be published  until the claims/payment process is complete.

3. Admin receives email advising a claim is being made.

4.0 Admin alters listing parameters in Mtree Backend for the listing being claimed
Before Admin Approves the Claim you need to change some properties in the Listing. Basically you need to set the listing parameters so it will generate the payment buttons. For this you need to change the Parameters so the Listing Equals a NEW LISTING as shown in the PaymentsPlus 2.25 User manual on Page 44.

If the Listing was added by Admin via the Front End, then the product ID will have already been set and the listing can be Edited via Mtree's Backend for the Listing

Set Approved = NO
Set Published = NO
Set Publish Up =  0000-00-00 00:00:00
Set Publish Down =  0000-00-00 00:00:00

If the listing was added by Admin via Mtree's back End or Imported using Mtree's import component or other SQL file, then you'll need to modify the listing using PhpMyAdmin.
Firstly you'll need the the Listing ID, you can get this by hovering your cursor over the Claims link in Mtree backend and read it from the progress bar in your browser. Lets asume the ID was 1234 and your database prefix is jos. You also need to know the PaymentsPlus product ID that you want to apply to the listing, remember that the Listing Type has already been set, so you need to identify what Product you have that's associated with the Listing Type. Lets assume the product ID was 3 and related to a Free product therefore the the Listing Type would be 0 (Free = 0, Featured = 1, Standard = 2)

In PhpMy Sql run the following SQL:
Obviouslly you'll change the link ID and product ID to suit the other parameters however need to be as shown to generate the pay buttons for a NEW LISTING.
SELECT * FROM `jos_mt_links` WHERE `link_id` = '1234'
Then edit the following fields, note all the values are numeric NOT text.

Set link_published = 0
Set link_approved = 0
Set publish_up =  0000-00-00 00:00:00
Set publish_down =  0000-00-00 00:00:00
Set link_featured = 0
Set ipn_product_id = 3
SAVE

5.0 Admin then approves the listing.
This changes the owner from Admin to the Users Username/ID. Email is sent to user advising the claim is complete. You should change the email text to advise the that whilst the claim has been approved, the listing is now not visable to the general public and they now need to pay for the listing, If its payable OR confirm the listing if its a free one. It is this process that adds the vital info into the listing in Mtree and creates the subscription in PaymentsPlus.  You might also like to mention the My Page link in mod_mtree_menu will take them to their My Page.

IF this process is avoided then when the User or Admin tries to edit the listing from the front end a php error will show simply because the vital info PP needs is missing thus the add/edit listing template can't generate correctly.

After the user follows the payments process the subscription will then show in PaymentsPlus Manage Subscriptions. And if its a Free or Offline Payment will need to be processed by Admin accordingly.

It is highly advisable to alter all the texts in both the claims form and the emails being generated, generally this is done in the Mtree language file. Note make sure you save this somewhere safe because an upgrade of Mtree or PaymentsPlus may loose this and if so you'll need to re-apply it after an upgrade.