Fix 1 (from user sneezybusy):

Hello Guys! I’ve had the same issue with my donation page. After submit the contact form, a message informed me that the email was sent, but after checking my mailbox several times, I was still unable to receive it.

After extended searching I found the solution and it was simple. Don’t use GMail (@gmail.com), neither mailboxes handled by any other provider who uses “Sender Policy Framework” (SPF) check, as GMail does. It has been reported that even AOL, Yahoo and Hotmail use SPF.

This problem is nearly always related to the anti-spam policy of your provider who handle the mailbox where you aspect to receive the submissions. So, the best way to avoid the problem is to change your email address. Now, it works!

I hope it will help for your successful fundraising.

Fix 2 (from the plugin’s original author):

Please check your log (under Seamless Donations > Log in WordPress Admin).

If it shows Pending – then your PayPal account is not approving the payments. Make sure you:

1) have verified your PayPal account – check and confirm that your PayPal account has a verified email address. If the address in your PayPal account is not verified, payments will not automatically be marked as complete.
2) do NOT have Payment Review enabled on your PayPal account
3) have set up the currency in PayPal to match the currency you have set up Seamless Donations to receive in
4) if the donor elected eCheck – those can take several days to clear – and until that happens it will show pending

Fix 3 (from one of our users):

Check the email address. You may have misspelled it. Yes, it happens!

Fix 4:

Try disabling W3 Total Cache (or other cache plugins).