There hiring process sucks, and that tends to be the generally consensus around Glassdoor for this company. Unfortunately there process is one where they ask you a question and unless your solution uses proper technique or you tell them what they want to hear your crap out of luck. I would say it good experience none the less just so you get an idea what these tech interviews are like.
I would encourage anyone who is interviewing to not loose out hope and think you are not qualified. The fact they called you and might have made a couple rounds shows that you are. It just means that someone else might have just been better than you on that date is all and not just in getting the answer but in how they approached the problem.
Currently have made 2nd rounds 5 times at different companies made finals at 2 of these companies and received 1 offer from said companies.
Leetcode,HackerRank, CodeFights and geeksforgeeks are great resources.
Also focus more on practicing approach than just solution, Cracking the Coding Interview has a good section on that. Good Luck!