"I cannot sleep in this bed."
Translation:Eu não consigo dormir nesta cama.
I think "I may not sleep in this bed" would be better if the sentence used "posso", suggesting that you don't have perimission to sleep on that bed. What helped me with those two words was to picture "conseguir" as "manage" suggesting a context of "ability" like for example in this sentence, it means that whoever it is that's speaking, didn't manage to sleep on that particular bed. Just like if you couldn't manage to find your wallet you'd say "Eu não consegui encontrar a minha carteira"