Windows Insider team is now working on Windows 10 Redstone 2 build 14906 in the internal ring. Windows 10 R2 build 14906 and Mobile build 10.0.14906.1001 were compiled on August 13, 2016. Microsoft has already released first Windows 10 Redstone 2 build 14901 for fast ring insiders members. If insider build does not show up for you, here is the fix.
Microsoft also shared an information related to Redstone 2 build. Microsoft will release Windows 10 Mobile Redstone 2 build next month. Windows 10 Mobile Anniversary Update build 10.0.14393 is expected to release very soon.
