When copying and pasting a deck on iPhone, I see the “Pasted from Safari” text at the top, but never get the confirmation pop-up to paste the deck. This happened last week as well, but then was working again over the weekend.
It’s the same for me, it really pisses me off. No deck is inserted
Are you absolutely sure the deck code is valid? Where did you get it?
Some third-party websites will give bad deck codes that contain invalid cards (Zilliax with no modules selected, or ETC Band manager with an empty sideboard), and the game correctly refuses to recognize the code.
Try pasting the deck code into an online deck viewer, to see if it has mistakes like that.