Can't a pawn capture onto the last rank to promote? I do not play chess much. Recently a friend reached out to play some online games.   We ran into an odd situation that I cannot find a rule on.
His White pawn was at g2 and my Rook was still at h1. He planned to take the rook with his pawn to promote it, but the game would not allow him to make the move and we couldn't figure out why.
Is there something illegal about that move? There were no underlying issues with the pawn movement that would leave the king in check or something similar.
Addendum-Per the answer below, I asked him about popups getting blocked. He said he had no problem getting the promotion going forward, but was being blocked from taking the rook.
Since the board is mirrored, the pawn is on b7 and the rook on a8. But b7xa8 promoting to a piece is a valid move.
I'm not sure which program/website this is, but it could be that a popup is asking to which piece White wants to promote, and something/your browser is blocking this popup, and your friend cannot complete the move.