On Rupeezy's market depth screen, a 0 at a bid or ask level means there are no live orders waiting at that price right now. The market depth screen shows the real buy and sell orders resting in the order book — so when a level reads 0, nobody is currently queued there. It's a reflection of the market, not an app error. Three situations cause it.
Why does market depth show 0 when the market is closed?
Outside trading hours the order book is empty, so every level shows 0 until orders start coming in. Depth fills up once the market opens — see What are the equity market trading hours?
Why does an illiquid stock or option show 0?
A thinly traded stock or a far out-of-the-money option may have few or no resting orders, so some or all five levels show 0 even during market hours. There simply aren't enough buyers and sellers queued — see What is liquidity in the stock market?
Why does one side show 0 when a stock hits its circuit?
When a stock hits its upper circuit there are no sellers left, so the ask (sell) side goes to 0; at the lower circuit there are no buyers, so the bid (buy) side goes to 0. One side of the book empties until the price unlocks — see What are circuit limits or price bands?