PayPal - "Problems with seller's site..."

I produced a classic PayPal button with a drop down menu for pricing options. All my tests took me to PayPal.

My end user reported receiving "Problems with seller's site".

I created a new button and unchecked the hosted at PayPal option in step 2.

The problem seem to be solved, but I needed to know why both buttons worked for me and not the end user.

I found that recreating the button as not hosted at PayPal was not the correct solution.

The correct solution was to remove the special characters in one of the menu options, which read "Individual (Ltd. Qty).".

Lesson: do not use special characters in the labels for any pricing option.

Create a Pay Pal Sandbox Button

In order to create a test PayPal "Buy Now" button, follow these steps.

Create a real PayPal account.

https://www.paypal.com

Login to PayPal's developer platform with credentials from step 1.

https://www.developer.paypal.com

Click through Dashboard | Sandbox->Accts and you should see a similar screen.

The facilitator account is a test merchant that is automatically generated.

Create a fictitious personal account for testing.

Click on the facilitator merchant account to view the profile, which has login credentials.

Click "Enter Sandbox site" and login with the facilitator credentials.

https://www.sandbox.paypal.com

Click Merchant Services tab and then My Saved Buttons.

You will notice that the link takes you to PayPal production.

Change the URL in the browser address field to include "Sandbox" qualifier, e.g.

www.sandbox.paypal.com/c2/cgi-bin/webscr?cmd=_button-management

This could fail several times before working.

Make sure that your browser is pointing to sandbox when you finally get a "My Saved Buttons" screen.

Click on create buttons, make sure the browser is pointing to sandbox and follow instructions.

Eventually paste the HTML code into your website and pay with the personal sandbox account.

I suppose I can make a cURL or a Python script to do all this.