I first began chess by playing online. I did this for a few years before playing someone on a board.
It's hard at first because you're not used to seeing it in 3D.
Older players had the reverse problem. They played and analyzed on boards all their life and had trouble switching to the 2D of online.
But after you get used to it, and you play once a week on a real board, there's no difference.
The initial stage of getting used to it does take some time (maybe a week or two?)
I recommend setting up tactic puzzles on a board and solving them. If you play daily games here try setting up your position on a board and analyzing it like that.
I’m curious to know if anyone has had trouble translating their skill from online to OTB? For example has anyone made massive improvements in their game online but failed to bring it to the chess board?