IGG please note which version this is. Build 18 is Full Release and happened in May and the latest is build 20 which is from September. I guess the only way to find out is to hope the dev marks his versions in-game...
EDIT: Yep, looks like it's an obsolete May release. Needs updating.
I think it could be one of the following 2 reasons:
Try updating the latest NET Framework for your windows (you can find it on the Microsoft site).
Maybe your AV blocked it, because recently AVs are actively blocking installers made from inno setup, fuck them. You can search the internet about this. (Besides, this release comes from the scene, so you can rest assured, you can check the file's validity by comparing the file's hash, use the predb site to see the code.) hash e.g. https://www.srrdb.com/browse/category:pc/order:date-desc/1
EDIT: Yep, looks like it's an obsolete May release. Needs updating.