No Paypal during checkout for 360-subscription?

I'm trying to book the 360/pro subscription, monthly payment. I can check in my account, I can choose the subscription, the process lets me decide to use Paypal, I check in Paypal, Paypal accepts the NI request and sends me back to the NI-site. I can check the "agree to terms" button- but I can not proceed. The "continue"-button stays greyed out. Tried that with three different browsers, no blockers active, cookies active or reset… no dice. Any idea? Thx in advance!