On the Tax Reports page I can see a "Review Needed" section and there's a message:
Did not find any wallets with issues (try deleting cache?)
Deleting browser cache and restarting gains
does not help
Solution
This error is usually caused by one of the two:
  1. "Missing purchase history" warning on untracked tokens or implausible trade
  2. Implausible transfer (merged a withdrawal that happens
    after
    the deposit)
Ad 1 - Can be found by generating a "Capital gains" report for the year.
Ad 2 - Not easy to find, usually need to browse through transfers and the "Ledger" tab to see where timestamps don't match