I think of four things:
[1] It is still adjusting and it may take several days, even a week+. (#3 and #4 are largely irrelevant then).
[2] Lone pictus will almost invariably be very shy and a hider. They do well in groups of say 6+, 12 is better. I have 27 in a 240 gal and they are a hoot. Loners would come out at night, so whatever's left over, they will pick up. If nothing's left over, it may make sense at least initially to leave some food for it at night and start getting it more used to light later after it has established itself in the tank and you are sure it is eating well. Dim light or no tank light, just a not too bright room light, should help too.
[3] Your water parameters matter - ammonia, nitrite, and nitrate. What are they and how do you measure them?
[4] Are there any other possible sources of stress? Is the aeration adequate? No bullying? Are pH, temp, hadrness within range and stable?