Hi,
For revaluation, the offset account should not be a reconciliation account. Previously, you set the account as the APC account, and it's wrong and system complains that you can not post to this account directly (the reconciliation account does not allow this).
You just imagine, by stetting the revaluation account and the offset account as the same account, what's the purpose of doing revaluation then, not mentioning the nature of the offset account.
Anyway, just from the technical point of view, this account should not be a reconciliation account.
Normally, this account is a temporary account, and the balance will be transferred to P/L or balance sheet equity account (revaluation surplus) based on the balance is debit/credit in the year end closing. Due to this, this account must allow manual posting.