Update It looks like some Windows 10 Mobile Fast ring Insiders are not getting the new preview build. Windows Insider head Dona Sarkar has posted on Twitter that the team is investigating this issue.

Update 2 As of 7 PM ET the "caching conflict" appears to be resolved and letting users get the update on Mobile

Microsoft has released the Windows 10 PC and Mobile preview build 14905 to members of the Insider testing program on the Fast update ring.

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In a blog post, Windows Insider head Dona Sarkar noted this was the first preview build for Windows 10 Mobile since the rollout of the Anniversary Update earlier this week. There's just one new feature in this build for Mobile users:

We are introducing a newly refined sound set in this build, uniting the best of our past and present. We aspire to set a new bar for mobile sound set quality, and are trying to make the soundscape of technology more beautiful and harmonious. This also helps align with new sound design direction of the Windows platform as a whole, so that mobile sounds will family with desktop and tablet and be feel instantly familiar to all Windows users. We will continue to evolve – head to Settings > Personalization > Sounds to see the updated list of available sounds and let us know what you think!

Windows 10 PC Fast ring Insiders will see the following fixes and improvements for build 14905:

  • We have fixed an issue causing a large blank space to appear between the address bar and web content after the address bar moves back to the top when opening a new tab in Microsoft Edge.
  • We have updated Narrator Scan mode for table navigation to now support CTRL + ALT + HOME to go to the beginning of the table CTRL + ALT + END to go to the end of the table.
  • Edge now supports the CTRL + O keyboard shortcut for setting focus to the address bar.
  • We fixed an issue resulting in Sketchpad and Screen Sketch crashing after trying to change the ink color twice in a row when the ruler was visible.

There are also several known issues with the PC preview build:

  • Support for kernel debugging over 1394 has been removed, but will be available in an upcoming kit release. A work-around will be posted to the Debugging Tools for Windows Blog shortly.
  • Adobe Acrobat Reader crashes when you try to launch it.
  • Cortana's text to speech capabilities is not working in this build. For example, Cortana won't be able to read text messages out loud for you, tell jokes, sing, or give verbal prompts.
  • When clicking on the power button on the Start menu, it closes the Start menu without opening the flyout with restart/shutdown options appearing. As a workaround – you can right-click on the Start button (or WIN + X) and choose to shutdown via this menu instead.
  • Apps such as Yahoo Mail, Trivia Crack, Google and the Skype Translator Preview app will crash in this build due to a compatibility issue from a recent platform change.
  • The Settings app may crash on certain editions of Windows 10 when navigating to different settings pages due to a missing .dll file. We are working on getting this fixed soon.

Windows 10 Mobile users will get a number of bug fixes and improvements with the preview build 14905:

  • Missed call notifications are now more actionable, with inline options to call back, text or remind yourself to do something about it later.
  • We fixed an issue where videos played in Windows Phone 8 apps might not pause when an incoming call was received.
  • We fixed an issue where, if "Show my caller ID" is set to "My contacts", the contact being called might still see a blocked caller ID.
  • We fixed an issue where the Lock screen might fail to update to the new time after a time zone change.
  • fixed an issue resulting in music not resuming after a call was finished, if Turn-by-Turn directions were being read out from the Maps app when the phone call came in.

There are a couple of known issues in the new Mobile preview build

  • If you move apps between a SD card and internal storage (either direction), those apps will get stuck in a pending state. The workaround to get your apps working again is to uninstall the app through Settings > System > Storage (apps cannot be uninstalled from All apps list). Then you can re-install the app from the Store.
  • Cortana's text to speech capabilities is not working in this build. For example, Cortana won't be able to read text messages out loud for you, tell jokes, sing, or give verbal prompts.