So it happened to me also. Deposited 500 Euro into Kraken's Fidor account through SEPA and it got stuck with status "on hold". Transfer was done from Consorsbank in Germany, I am Tier 3 verified.
I googled and found a lot of alarming stories from many, but there is nothing really to worry. I opened a support ticket and within 30 mins got told that there are some regulatory issues and they need additional ID confirmation (pic with one holding the ID and some piece of paper stating it is for Kraken).
This took a bit longer as it is not so easy to get a high resolution pic on ones phone doing it alone, but I managed it.
Account got verified and funds were released. Overall time 2 days.
So don't listen to everything that people tell you in the webz. Great support from Kraken, thanks guys!
(alternatively, the solution may be to contact them through their reddit channel with the corresponding ticket number)