Another update:

Geekwire has a statement from Paypal confirming the OFAC issue:

"As a US company, PayPal has to comply with US government OFAC sanctions. Payments that may potentially violate US sanction laws may be placed under review instead of automatically declined. Our goal is to deliver seamless payment experiences, and it is never our intent to hinder legitimate business operations. If, upon review, there is nothing in the payment that indicates it might violate the law, the payment will be processed. We realize any delay in making or receiving a payment can be frustrating, and appreciate our customers patience as we work to meet our compliance obligations."

There's an opinion piece in Spiked about this today.

"It’s hard not to feel a bit sorry for social-justice warriors – it must be exhausting finding things to be offended by. The latest is an advert reading ‘I ♥ JK Rowling’, which was paid for by the campaign group Standing for Women. This fairly innocuous message, displayed to mark the birthday of the best-selling author, has now been removed by Network Rail following online complaints of transphobia."

https://www.spiked-online.com/2020/07/31/the-genius-of-the-i-heart-jk-ro...

The billboard has been removed. Apparently it's against the media company's "code of acceptance for advertising" to love JK Rowling.
https://www.adland.tv/adnews/i-jk-rowling-billboard-has-been-removed-net...