If the class is not recorded for attendees or you happen to delete recording for the attendees then in that case recording is not accessible to the attendees (users who attended the class or who were invited later to view the recording). This is due to because currently the recording gets enabled for all the attendees or for none. We are working on bringing the feature to set recording permissions for individual attendee then you would be able to do so. For the time being if you wish to invite persons to view the recording, record the classes for the attendees too (set it while scheduling the class) and then you can invite the users to view the recording.
You may send them the common session link to view the recording. This was the recording can be openly and freely shared further by the persons you invite. Or you may personally invite them entering their email ids or through your webmail or WizIQ contacts. Through this mode, only the invited person has access to view the recording and he/she cannot share it further.