Your uploaded presentation is blocked and cannot be made private as you have already consumed 100 MB private storage space allowed in your free account. You can do any of the following:

As a guest uploader, you can instantly upload and get the URL as well as the embed code of your presentations,but you can't use the following services:Also all guest uploads are available for download by default. We suggest you to upload as a registered user to access all the features and protect the privacy of your file.

By setting passcode expiry you are able to automate how long the private presentation is available for viewing. This gives you control over whose viewing your content and you can also manage the length of time when someone has access to the presentation. For instance, if you’ve set 2 days and 2 hours as time duration for viewing a presentation, the passcode will expire once the duration is over. You can reset the old passcode along with the time duration to allow the same contacts to view the presentation. You can even set a new passcode and invite more contacts to view the presentation.