So one of my players had a new character, and so I deleted his Journal character sheet and token on map, and replaced them with new ones assigned to his player name as normal. At this point he could no longer see anything, nor could another player, whose character had been under the first players control the previous week (and I had not removed that control link in the Journal yet). In the end it was necessary for both players to delete their accounts on Roll20 and re-create them, then be reassigned to their characters. It seemed as if the system could not assign the player to his new character token (and hence see the dynamic lighting effects) even though the player was definitely in game and appeared in all the look up lists for assignment. Presumable the second player was also affected because the first one was in control of their character when we did the change. No idea why this happened, but re-creating the user accounts fixed the issue, though they need to recreate the macros that they had built at the account level.
