Have a place to download 1.55 then.
Or remove the 'lol cant install' feature of 1.56, have it be just a warning like before.
But no, that would hurt sales, everyone who hates the start menu already bought Start8, so gotta get them to buy Start10 now even though they should be the same product.
Unfortunately people install and would then complain which results in support costs. We used to give some products away free with a clear message about no support and people ruined it by asking for support and so using up valuable resources.
Development for Windows 10 is not free and there was considerable work put into Start10. It is not Start8 with the 8 replaced with a 10 and an if on Win10 do not run line removed.
I should stress that the reason Start8 is not working correctly on Windows 10 is due to changes in the OS itself. We did not put any code in to stop it working (other than the installer now blocking - which is a simple OS check that compatibility settings would bypass), it got broken due to things outside our control and only works as well as it does because we had done some initial work on Windows 10 support in the early Win10 beta time.
The November update to Windows 10 broke Start8 further which I think if you recently upgraded to Windows 10 will install on your computer 30 days after you upgraded to Windows 10.
If you are using Windows 8/8.1 then Start8 is the product for you, but if you want to use Windows 10 then I strongly recommend Start10 as it actually supports that OS. If you want to force Start8 to run on Windows 10 then that's your choice, but be aware that we will offer no support at all for this and the response to any issues would be upgrade to Start10.