Sometimes coding is hard. You forget how to write code, and you forget how to solve problems. Maybe your mind is like a sieve that day.
When you get to that stage, stop. Your brain isn't working, perhaps your body isn't working as it should.
Instead take a break, go for a walk, do a chore, let your subconscious churn in the background. Try talking to a rubber duck, or drawing the issue down. Do something different.
If that's all not working, try writing some prototypes. Allow it to be bad, allow it to be rushed, but just start getting some words down.
Recollect how many times you've figured out the solution in the shower or in bed. Taking space is a good thing.