Hey there! To minimize confusion because troubleshooting may be different for preview updates than regular versions, you'll want to post this, and everything else preview related in the preview forums (forums.xbox.com/.../default.aspx).
This will also ensure that the proper team sees your post and can help you out. Also, make sure you look at the list of known issues to see if there is a workaround.
If you haven't already, be sure to report any issues via the preview app on your console, so that all relevant data gets reported to Microsoft.
For most issues, a hard reset will help. Hold the Xbox logo on the front of your console for 10 seconds until it fully shuts down. Wait a few seconds, turn it back on, and try again.
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