I am getting the same problem, Error 520 on login. 2 Days ago I was able to get inside, but after clicking on withdraw euro or BTC,... you guessed right, error 520.
This thing makes me feel pretty nervous and worried, I am afraid for my funds and coins. I think I am done with them after I withdraw everything (hope I will be able to).They are going to lose like half of their customers. This is taking for too much long.
They acknowledged the serious problems with a recent blog post:
This blaze is on fire.
The recent, unexpected explosion in demand has been overwhelming.
Each of the past few days has produced 50,000 new account registrations and 10,000 new support tickets —
an order of magnitude above where we were just last quarter. Concurrent users, daily trades and volumes are
also hitting new all-time highs. We are struggling to keep up.
Kraken.com performance is extremely degraded and unreliable. Clients can expect severe latency and
difficulty interacting with all web and API services. Requests will frequently timeout and fail.
At the moment, the only solution is to wait and try again later.
Next week we will be rolling out a major systems upgrade which should resolve these scaling and load issues.
The upgrade is long overdue and has been substantially delayed by the diversion of resources toward
the protracted fire fighting effort required to deal with the last several months of unrelenting growth.
I hope that the roll out of the "major systems upgrade" will finally fix these issues once and for all.
I understand that they are overwhelmed by the surge in account registrations, but their platform has
been an unusable mess even before the recent surge in trading activity.
At the moment I can´t submit a trade and get a Cloudflare error literally every second pageload at Kraken.
In the meantime, Bittrex, which has been working MUCH better than Kraken, has halted their new user registrations. Suggest you follow suit! At least it would signal to your users that you are taking the problems seriously! 
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