This is weird. You should be able to jump on that gray platform with no problems. All rooms were designed to be fully navigable. Maybe it is a bug on your jump, I will try to find out the issue, if you have any more information that can help me out please let me know. Thanks!
The best I can say about my situation is that I eventually was able to buy the upgrade that says "pressing and holding the A button lets you jump higher," but even after buying the upgrade in the meta-progression shop, the robot still couldn't reach the platform. Is it possible that can be due to a weak graphics card, low FPS, etc. since my computer is a regular old computer, not a fancy one like the faster gaming computers you might see at a store?
Then again, the way platforms were handled on my end is that even when I was directly under gray platforms and just standing under them (no moving), the character still couldn't reach them, and maybe the game on my end is making the gray platforms higher then they should be on either lower resolution or weaker graphics cards, since I have hear that weaker graphic cards and low FPS can cause more bugs and issues then higher performance computer, which some people don't own. Could that be a cause, if possible?