@Sam Blackwood , I believe you are talking about resetting the password for your users in On-Prem Active Directory. If yes, then you wont be able to reset the password until the machine on which user is trying to reset the password is able to speak to a domain controller in your domain. Also, the password would expire based on the password expiry time limit set in your group policies.
In case users are not connected to the domain, they might not be able to find out that their password has already expired, but once they get connected back to their domain, then the old passwords would fail since already expired.
One solution is to deploy VPN solutions so that when users are working from home they can connect to VPN which would allow them to get connected to your internal organization network and they can reset their password as an when required even while working from home.
Hope this helps.
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