Subject says it all.  I went back to 1.5.3, didn't bother even trying 1.5.4.
 

According to UVI Falcon is comparable with Windows 8 or above.

COMPATIBILITY

Stand-alone, VST, AU, AAX, Windows (8+), Mac (OS X 10.8+), we've got you covered. Falcon's core has been optimized for efficient performance on all popular platforms and DAWs

See:

https://www.uvi.net/en/instruments/falcon.html#tech-specs

They changed the supported platforms list.  Windows 7 was supported up until this last release.  They didn't add anything about this change to their release notes.  1.5.3 works just fine in Windows 7.
 
 
 
 

I understand not wanting to upgrade to Win 10, but Win 8.1 (which is basically just a better optimized Win 7) has been rock solid for ages, and would solve this problem and buy you a few more years of compatibility/support.
 
Last I checked (a couple months back) on Ebay, there were a number of OEM licenses (for Win 7 and Win 8.1) selling in the $10-30 range.  You get a valid product key immediately emailed to you.  The OS installers are freely downloadable from Microsoft.
 
I purchased a license each for 8.1 and 10 (about $12 per), and have since loaded them on systems for friends/family.  I plan to grab a couple more soon as spares.

I wrote to my contact at UVI and she replied that Win 7 is no longer officially supported, but UVI will continue to try to maintain compatibility of their products with Win 7 (but apparently don't always succeed).
 
However, this is wrong.  Microsoft is fully dropping support for Win 7 in Jan. of 2020.  They may not be doing new development, but they are continuing to fix bugs and address security issues and will do so for the next 17 months or so.

It looks like some sort of compatibility issue with the Pace support DLL they extract into your tmp directory when it starts.  I suspect they may have broke this more by carelessness than by design.  There are only a handful of APIs that have been added post Win 7, few(none in my opinion) of which are worth breaking compatibility for.   I didn't bother looking that hard at it though to see what exactly the problem is and have no plans to re-install it.
 
I just wish they would fix their installer to tell you it can't be used on Win 7, rather than let you install it and then find out it won't run.  Their website doesn't have historical downloads so if you weren't planning ahead you could easily get stuck.  Which is the only reason I bothered posting this.
 
Most users should certainly consider upgrading to Windows 10, you won't get any argument from me on that.

I also couldn’t run Falcon 1.5.5 on my Windows 7 machine, so I sent UVI a (not very nice) support ticked. And sure enough, within a day I had gotten two test versions of 1.5.6 where the latter worked both in stand-alone and plug-in mode on my system. Unless they have some additional issues to solve, I would expect it to turn up quite soon on their product page.
 
It seems to me as if UVI in reality haven’t dropped support for Windows 7 although they officially say so on their Technical Specifications page. And when it comes to quick support UVI is absolutely top-notch.

And now version 1.5.6 is available for download at UVI. I haven't bothered to download it myself, as I assume it is the same version as I received yesterday (and I'm currently on a snail-pace internet connection). But as the pre-release worked fine on my Windows 7 system I don't expect this official version not to do so.
 
According to support they'd added compatibility with Windows 8.1 SDK in Visual Studio 2017 which unfortunately made the code break on Windows 7 systems.
 

Canopus
And now version 1.5.6 is available for download at UVI. I haven't bothered to download it myself, as I assume it is the same version as I received yesterday (and I'm currently on a snail-pace internet connection). But as the pre-release worked fine on my Windows 7 system I don't expect this official version not to do so.

 
Good to know.  Thanks for the update.