The takeaway is: each private key can generate 2 versions of Bitcoin address, compressed and uncompressed. When you stare at a Bitcoin address, you CAN'T tell whether it is compressed or not, so you have to check the balance of both versions for a single private key.
afaik, each Private Key (Hex Format) can generate 4 valid bitcoin addresses in 3 address formats (P2PKH, P2SH, Bech32)
1 is derived from uncompressed public key, and 3 more from compressed public key
for example,
Private Key Hexadecimal Format: 0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF
Private Key WIF uncompressed:
5HpneLQNKrcznVCQpzodYwAmZ4AoHeyjuRf9iAHAa498rP5kuWbPublic Key uncompressed: 044646AE5047316B4230D0086C8ACEC687F00B1CD9D1DC634F6CB358AC0A9A8FFFFE77B4DD0A4BF
B95851F3B7355C781DD60F8418FC8A65D14907AFF47C903A559
P2PKH (legacy) uncompressed :
1CLrrRUwXswyF2EVAtuXyqdk4qb8DSUHCXPrivate Key WIF compressed:
KwFvTne98E1t3mTNAr8pKx67eUzFJWdSNPqPSfxMEtrueW7PcQzPublic Key compressed: 034646AE5047316B4230D0086C8ACEC687F00B1CD9D1DC634F6CB358AC0A9A8FFF
P2PKH (legacy) compressed:
1M8Qk46ERsPrEtWLBRSET5NUH2Ck5wwREUP2SH Segwit Address:
31khcn4aNFxMdvcVUCHj8Z1u1A7CqBqyArBech32 Address:
bc1qmnyn7x24xj6vraxeeq56dfkxa009tvhgqffstc