It's probably that you reached the max number of users you can block(200). I can block him just fine.
Can't Block User? WassupMr Macer?

I see Wanmokewan thank you for answering since Mr. Macer is ignoring me. Now I get it.
Actually, please ignore what he said. Judging from the fact that your rating is no longer stuck in the 900s, it seems that my advice to you last time on dealing with the 3-headed hyena-fiend has worked - so you know the level of expertise that I have. In response to your current inquiry, the answer has nothing to do with whether the user in question is or is not a mod. Rather, by all appearances it appears that she has cast a black lightning incantation ritual on herself, which prevents other people from blocking her on chess.com (or on any other site for that matter). To negate the ritual so that you can block her, you must take the following steps.
1. Go to a secluded place in the woods, where you can stay for an hour or so without being seen by another human being (because if you are seen by anyone at any point during the process you are about to complete, it will end in failure).
2. With an axe, cut down enough branches from the trees to sustain a fire for an hour.
3. Put all of the firewood that you now have in a pile. Add some dry leaves to the pile, and start a fire by rubbing two sticks together. DO NOT use a lighter or any other mechanism.
4. Once you have the fire going, take off your clothes and throw them in the fire. Then, for the next 30 minutes, dance around the fire while continously chanting the following words: Fee fi fo fum! Your black lightning incantation ritual can kiss my bum!
5. After that, for the next 20 minutes, do a handstand next to the fire. Your feet must not touch the ground at any point during that time... so if you think you might have some difficulties, do some workouts beforehand to make sure you are prepared.
6. Now, for the final 10 minutes, climb onto a tree from which you can see the fire, and simply watch it. At the end of exactly 10 minutes, the fire will suddenly go out, and a puff of smoke in the shape of a lightning bolt will emerge from the ashes and quickly dissipate. At this point, you can get down from the tree and go back home, where you can then log on to chess.com, and block the user in question.
If you have questions about any of these steps, please let me know, as being precise is important in an endeavor of this kind. If not, then best of luck, and let me know once you have completed the process and succeeded in your blocking attempt.
Dear Mr. Macer: There is one particular parasite I am unable to block. Could you please explain why when I try to block that user I'm told "You Cannot Block That User". Why is that the case? have no desire to interact with that problematic character. It's disgusting that I can't block "her". Could you please tell me how I can get around this obstacle. I see no reason why a user cannot block another user especially a habitual harasser like "her". Please respond Mr. Macer.