Why a balance can show zero after you received bitcoin
A Bitcoin payment is not in a balance the moment someone presses Send. It has to reach the network, wait its turn and be confirmed in a block. Until then this report excludes it from the confirmed balance. A Pending note appears when the source reports a nonzero net unconfirmed amount. And a wallet has many addresses, so the coins may well have landed on a different one than the one you are looking at.
Check the pending line first
When the source reports a net incoming unconfirmed amount, the report's Chain notes show the line Incoming transaction awaiting confirmation
. The balance counts the payment once a block includes it. Blocks arrive about every ten minutes on average, but that is not a confirmation deadline. Timing depends on the fee rate and competing transactions, and a low-fee payment can wait much longer. See activity and pending transactions.
It may be on another address
A wallet hands out a fresh address for each payment and shows all of them as one total. An address report shows one address. If the sender used an address you gave them earlier, or your wallet showed a different address than the one you are checking, the coins are in your wallet but not on this address. See why one address is not a whole wallet.
It may never have left the sender
If the report shows no pending line and the transaction list has nothing new, this source is not currently showing the payment. That does not prove no node has seen it: the source may be delayed or incomplete, or incoming and outgoing unconfirmed amounts may cancel out. The common reasons are on the sender's side: the transaction was never broadcast, it was replaced by another one, it waited so long with a low fee that nodes forgot it, or it went to a different address. A mistyped address is normally rejected by the address checksum, but a different valid address is not. Ask the sender for the transaction ID and look that up.
What it does not mean
A zero on one address does not by itself mean the coins are lost; they may be on another address or have been spent. A pending payment is not necessarily a failed payment. A transaction disappearing from one node's mempool does not cancel it everywhere: another node may still relay it or a miner may confirm it. Check the transaction and your wallet before creating another payment.
What you can do
Refresh the report and read the Chain notes. Check which address the payment was sent to, against the one you are looking at. Ask for the transaction ID: the report of any address it touched lists it once it is confirmed. If you are the sender, your wallet shows whether the transaction was broadcast and what fee it paid.
Common questions
How long can a payment stay pending?
There is no fixed deadline. A low-fee transaction can wait for days. Bitcoin Core defaults to expiring mempool entries after two weeks, but nodes can use different settings and transactions may be rebroadcast. Expiry on one node does not prove a payment has been cancelled.
Does the report count unconfirmed coins in the balance?
No. The balance counts confirmed unspent outputs. A Pending note describes a nonzero net unconfirmed amount reported by the source; its absence does not rule out every pending transaction.
The sender says it went through. Why is it not here?
It may have gone to another address, still be unconfirmed, or be missing from this source. Compare the address they paid with the one you are checking, and use the transaction ID to check its outputs and confirmation status.