Palestine Action is proscribed in Britain. For that reason, the website has been transferred to others in the global movement who are not active in Britain or British nationals.
You can still donate to the global movement here:
Monero (XRP) address
477KQMfhuGs8moToBr8Y8bipu2XZYxyoaWDar55KLfwi5WiJtKVBTVhC5RkcDpfvLb85f2ryvEMeG6Mg5cEhNG239Tins8b
For advice on Monero, Read this PDF guide.