In reconciliation yes in accepting it noThe passive voice means the subject is being acted upon, so God by His imperative via the Gospel Truth is causing them to believe the Truth of their reconciliation, hence His command is backed up by His Power to produce the result of faith. Also the ones to whom this imperative is issued to are already regenerated new creatures in Christ vs 17. Has nothing to do with unregenerate spiritually dead sinners.
Doug correctly noted they were to submit to the reconciliation of God
2 Corinthians 5:20 (UASV) — 20 Therefore, we are ambassadors for Christ, as though God were making an appeal through us; we beg you on behalf of Christ, be reconciled to God.
Reconciliation was made on their behalf. They had no part in making it. They did have as part in accepting it
As though God did beseech you by us. Our message is to be regarded as the message of God. It is God who speaks. What we say to you is said in his name and on his authority, and should be received with the respect which is due to a message directly from God. The gospel message is God speaking to men through the ministry, and entreating them to be reconciled. This invests the message which the ministers of religion bear with infinite dignity and solemnity; and it makes it a fearful and awful thing to reject it.
Albert Barnes, Notes on the New Testament: II Corinthians & Galatians (ed. Robert Frew; London: Blackie & Son, 1884–1885), 132.