Timing of supply chests is confusing..
here is a supercell forum post which may explain:
From experience yesterday, stacking worked as follows for me.
The 24hr timer ran down and a chest became available to me at 6pm on wednesday. However I did not raid any bases and therefore did not earn the required vp to claim the chest.
I waited a further 24 hrs and started raiding bases at 6pm on thursday. After earning 5vp i collected wednesdays chest, at which point thursdays chest immediately became available. I then earned another 5vp and collected thursdays chest.
The timer restarted and i have to wait until 6pm this evening (friday) before todays chest becomes avaialbe to me.