If a Player1 is in an inventory menu (Personal, Chest, Crafting Table, etc) when Player2 player goes down to sleep, Player1 is unaware of the message as it is being hidden by the menu.
I would expect the message to persist for some time after leaving the inventory menu so that it is noticed.
I would like a personal preference at the length of persistence (10 seconds, 30 seconds, 1 minute, permanent).
Perhaps a status icon? By displaying the sleeping message, players are already alerted it is night; adding additional context (icons, persistent message) is not giving taking away from the game "rules".
Chat messages are not hidden by crafting/chest menus in Minecraft Java Edition.
Are you on the correct version of Minecraft? Does pressing F3 or FN+F3 show some debug information on your screen? If yes, then attach a screenshot with the F3 debug screen enabled.