sandbox donation ends as "pending"

Hi there,

I am brand new to Seamless Donations. I have done two test runs in sandbox mode, following David’s tutorial to the letter, and both times they end as “pending” with no donation appearing under “Donations”.

Here is the log:

[Seamless Donations Log Data]
2016-01-17 10:25:26 —————————————-
2016-01-17 10:25:26 PREPARING DONATION FORM
2016-01-17 10:25:26 Seamless Donations Version: 4.0.13
2016-01-17 10:25:26 User browser: Safari 9.0.2
2016-01-17 10:25:26 Assigning hidden field session ID to BAB08A3C-233F-02F6-2301-16EB611E4B9C
2016-01-17 10:25:26 Form action: http://swampscottlibraryfriends.org/wp-content/plugins/seamless-donations/seamless-donations-payment.php
2016-01-17 10:26:22 —————————————-
2016-01-17 10:26:22 DONATION TRANSACTION STARTED
2016-01-17 10:26:22 Test mode: A
2016-01-17 10:26:22 PHP Version: 5.4.40
2016-01-17 10:26:22 Seamless Donations Version: 4.0.13
2016-01-17 10:26:22 User browser: Safari 9.0.2
2016-01-17 10:26:22 IPN: http://swampscottlibraryfriends.org/wp-content/plugins/seamless-donations/dgx-donate-paypalstd-ipn.php
2016-01-17 10:26:22 Payment process nonce 30fe1eb08f validated.
2016-01-17 10:26:22 Session ID retrieved from _POST: BAB08A3C-233F-02F6-2301-16EB611E4B9C
2016-01-17 10:26:22 Looking for pre-existing session data (guid/audit db mode): BAB08A3C-233F-02F6-2301-16EB611E4B9C
2016-01-17 10:26:22 Duplicate session data not found. Payment process data assembly can proceed.
2016-01-17 10:26:22 Success URL: http://swampscottlibraryfriends.org/donate/?thanks=true
2016-01-17 10:26:22 Saving transaction data using guid/audit db mode
2016-01-17 10:26:22 Name: PayPal Demo
2016-01-17 10:26:22 Amount: 5
2016-01-17 10:26:22 Preparation complete. Entering PHP post code.
2016-01-17 10:26:22 Checking for repeat. REPEAT value is [].
2016-01-17 10:26:22 Computed RETURN value: 'http://swampscottlibraryfriends.org/donate/?thanks=true'
2016-01-17 10:26:22 Redirecting to PayPal… now!
2016-01-17 10:34:23 —————————————-
2016-01-17 10:34:23 PROCESSING PAYPAL IPN TRANSACTION
2016-01-17 10:34:23 Seamless Donations Version: 4.0.13
2016-01-17 10:34:24 IPN VERIFIED for session ID BAB08A3C-233F-02F6-2301-16EB611E4B9C
2016-01-17 10:34:24 PayPal reports payment status: Pending
2016-01-17 10:34:24 IPN processing complete.

Any insights much appreciated!

https://wordpress.org/plugins/seamless-donations/