

You could check to see if the “P trap” has removable fittings on each end, then it’s just like unthreading the coupling and clean out the obstruction. If not try the snake method already mentioned. It’s probably just hung up on some build up as the glass pieces should be fairly small to fit in the drain.
You could try using the plunger but make sure to disinfect first and then the sink after.
You could probably find a YouTube video to demonstrate, it should be a relatively easy fix.










Oh yeah should be a fairly simple task even if they had to change the P trap.