Error occurs on this screen:
boardgamearena.com/gamepanel?game=laserreflection&howtoplay_seemore=
Refreshing doesn't help.
The problem occurs every time and is easily reproducible.

To start a solo game by the old lobby, you have to select training mode in advance. If you tried to start a solo game in normal mode, you'd get an explaining message. It's this text from the BGA main page: "Solo mode for this game can only be played in Training mode"

When starting solo mode by the new lobby for other games (I tried it for "It's a wonderful world"), it automatically switches to training mode, so no error message is needed.

This automatic switch to training mode seems not to work for solo games of Reflection in the new lobby. Instead I get the error message: "Lower the number of players to "1" to select a solo game mode", which isn't really helpful when I have already set the player number to "solo" ("1" is not available). Astonishingly, this text is part not of the main page but of the game Reflection itself. So this seems to be a bug especially in Reflection.

ChrisUK, here a workaround for you: First set the game speed to training mode (leftmost position), then choose player number as "solo" and you can start your game. Or use the old lobby ("Play now") instead.

Duplicate: boardgamearena.com/bug?id=80055

You should select training mode to start a solo game.