In VoteCast there is a configuration option that allows absent members to vote. If this option is turned on, council members will be able to cast their vote during any open vote, regardless of whether or not they are marked absent.
If the configuration option is turned off and the clerk marks a council member absent during a vote, the council member will not be able to participate in that vote; however, they will have the option of participating in the next vote. If the clerk marks the council member as absent during a roll call, they will not be able to participate in any votes until a new roll call is taken or the clerk deselects the absent status from each individual vote.
If the council member is marked absent and unable to vote, you will receive a notification in the voting panel.