PolyClay

Here is the final response I got from PayPal... "This was not a PayPal issue. We have received several reports from European merchants reporting intermittent connectivity issues to our API endpoints. After investigation by our engineering teams, we were able to narrow this down to a bad hop on the (public Internet) route to our API endpoints. Specifically, three hops were dropping packets. As a result the connection was never established and you may have received a TCP network timeout. We are currently following up with the third-party providers of these routes. If it works again for you at this time, your own network provider may have decided to use a different route to reach our API endpoints."

I happened to check whether ebay was similarly blocked yesterday, as it's really the same company. It was. I suspect the block was actually over their heads and some other ebay/paypal network bods.

It has started working again for me today too! PayPal MTS still didn't actually look at the issue though.

I have joined this forum after googling exactly the same problem. Two days ago, PayPal suddenly blocked access from my server IP address, with no warning or explanation. I have made no changes to my site in months. A simple curl command to https://api-3t.paypal.com/nvp from a shell fails with a 'couldn't connect to host' and all API requests timeout. Like the rest of you, I found first and second-line support to be fairly useless. I have now sent an email to the MTS team, after finding they exist, but am not particularly hopeful of a speedy resolution. I think I am going to hit twitter with this is well and try and shame them into some action.