I have exactly the same issue. I have tried to use different browsers (chrome and edge), I have tried on three different computers. I have tried using my wifi at home, and going via the network provided by mu mobile phone. Still I end up at the same error page all the time:
The system is currently unavailable.
We are actively working to resolve the issue as soon as possible. Please accept our apologies for any inconvenience.NXP Semiconductors Customer Support
At first I could still use LPCXpresso without having to register, but now it seems like some time limitation has elapsed, so now I can not do anything.
