Yesterday when Microsoft released Windows 10 build 14901 for PCs, Dona Sarkar warned that it may take a few hours for the build to show up on everyone's PCs. The next morning, many Insiders found that it was still not available.
After some users offered workarounds - which may or may not have actually worked for some - and Microsoft reached out to Insiders to investigate, Dona Sarkar has confirmed that the issue has been fixed.
Jason, Program Manager on the Windows Insider Engineering team, also told Neowin that it may still take a bit of time for the build to show up for everyone, so if you don't see it quite yet, don't worry; it's coming soon.
Build 14901 didn't contain much in terms of new features, but it was the very first Redstone 2 build, making it a preview of the next big update to Windows 10. Non-Insiders won't see it until 2017, likely in the spring. If you're waiting for a Windows 10 Mobile Rs2 build, it will still be a few weeks.