I have that issue too. The issue is an itch issue. The problem is if your screen resolution is too small, the side bars from the itch webpage (the ones that say "add to collect" "rate for brackey's jam" are overlapping with the game, even if you aren't clicking them somehow the mouse is still registering as clicking outside the game window and the game goes inactive. You can fix it by increasing the resolution on your browser window so the black menu bars arent near the game. It's VERY annoying lol.
Thanks for enjoying our game and my reviews haha. As for how to get that many acorns, you just need to play a ton haha