Account already in use
System Program · Custom(0) · 0x0
custom program error: 0x0
What it means
The System Program was asked to create an account at an address that already exists.
What to do
Use a fresh address, or skip creation when the account is already there. For token accounts prefer the idempotent create instruction.
Have the transaction that failed with this?
Paste its signature. TxWhy shows the exact instruction and inner call that raised the error, and rebuilds the transaction when the cause is one it can fix (compute limit, expired blockhash, priority fee, stale swap quote).
Code 0 means something else in other programs
Custom codes are private to each program. Check which program actually raised it: it is the innermost failed call, not necessarily the program you called.