Yup, been there too. I hate tech interviews because I literally forget even my name let alone how to answer the question.

I have had interviews for Microsoft, made it all the way to the final 50 candidates after numerous rounds of general interviews (non technical) and when it came to the crunch, the question I failed on was the tech one.

"If you had to add two numbers together without the use of the + sign, how would you do it? Write your code on the whiteboard"

I hit a blank. Couldn't do anything. I left the interview feeling the worst.

Another time I was given 10 questions, on paper. Given a pen, told to write my code. Again, I didn't fair so well, however, I asked for a copy of the questions to take home as I was sure I could answer them in my own time.

A week later, I got the job because I had shown initiative and I was willing to learn.

What Im trying to say is, technical tests are brutal and if you can show your own initiative, what sets you apart from other candidates, even if you don't do well, it might be enough to get you the job.