The system tend to be slow at this time of the day so you might try a bit later.

Otherwise there are several ways to make reservations, depending on what route you want to book. 

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105

Thanks, I've been trying it all day. It seems the proceed to payment does not show up bright yellow allowing me  to click on it even though all the info is there and I've ticked the accept terms and condition box.

Hello, we're sorry that you had troubles with making reservations. This was likely caused to a server issue that we experienced with our reservation system at the time. For future reference, it might be useful to know that you can make reservations using an alternative method as explained on our website or over here on the community.