14 DAY TRIAL // Microsoft released a few days ago another Windows 10 Mobile Technical Preview, which is supposed to expand compatibility to additional smartphones like Lumia Icon, Lumia 930 and HTC One M8 for Windows.
However, users report that they have trouble upgrading to Windows 10 Mobile build 10080 on at least two devices: Microsoft Lumia 640 and HTC One M8 for Windows.
We already know that HTC One M8 running Windows Phone 8.1 Update 2 (version 8.10.15143.154) will not be able to upgrade to Windows 10 Mobile build 10080 for the moment. The information has been confirmed by Microsoft, so there's nothing to do but wait for a fix.
The other smartphone that has issues when people are trying to install the latest Windows 10 Mobile Technical Preview build is the Lumia 640.
Many Lumia 640 owners have taken it to Microsoft's support forums to report that Windows 10 Mobile build 10080 does not show on their smartphones even though they have opted for Fast Ring updates.
The good news is Microsoft is already aware of the problem and has explained what's causing the issue and confirmed they are working to fix it.
Two Lumia 640 variants are affected by the issue
According to Microsoft, “to get from WP8 up to Win10, there has to be a software update path created. When an update is made available on the server, your on-device OS checks to see where you are currently (what version it has), where you'll be going (what is new on the server), and it validates that there is a valid path between the two.
“To over-simplify it, think of being in city A (WP 8.1), wanting to go to city B (Win10), and having a map that shows your device how to get there (the update path). The issue for users hitting the current ‘no build’ situation... is that there's no map in place. The software update path from your current OS build up to the new Win10 build is not in place yet.”
Only Lumia 640 devices that run software version 8.10.15127.138 or 8.10.15135.146 are affected by the issue, so if you own one of these variants, you won't be able to install Windows 10 Mobile build 10080 just yet.
As mentioned earlier, Microsoft has stated that they know about the issue and they are working to build in the update a path to make it available for these Lumia 640 devices as well.
However, it looks like it's going to take a bit of work to complete this, so there's no telling when exactly a fix for this problem will be released.