My wallet shows a different address every time: is that normal?
You open your wallet to receive and see an address you never wrote down: your stomach drops because it looks like something broke, you lost access, or you are being scammed.
**Every new address is derived from the same seed, not a separate account: your previous addresses are still yours and work forever.**
Why you see a different address
Your wallet is hierarchical: from your seed come a huge number of addresses. Showing a new one each time is expected behavior, not a failure. Source: BIP-32/BIP-44 + docs de cualquier wallet HD.
That makes it hard for anyone watching the chain to tie all your activity to a single label. It is privacy by design.
Old addresses are not deleted
The address you used yesterday is still tied to your seed. If someone sends bitcoin there, the wallet shows it just the same, even if it now offers you a different one for receiving.
There is no expiration date: as long as you have your seed, that address and every address you have already generated belong to you.
What to do if someone already sent to an old address
Nothing. You do not need to claim, import, or recover that address. The wallet knows it even if it does not display it on the main screen.
If you want peace of mind, look for the transaction you already received there in the wallet history; the balance is with you.
Old addresses working does not mean reusing them is smart
Your previous addresses still belong to you, but using them again to receive exposes you more than necessary. The whole point of a fresh address is so you never have to reuse one.
Source: BIP-32/BIP-44 + docs de cualquier wallet HD