and then creating an exe for the updates.
If I understand correctly here, you have created your own custom executable that downloads the MSI and the launches it in order to perform an upgrade?
If so, please make sure that on the machine where this is failing, there isn't any software that is blocking your executable from downloading the MSI (e.g. a Windows Firewall rule, an AntiVirus software).
Other than that, you can try to customize your executable to create a log file with some common steps (for instance, when it tries to download the MSI, when it tries to launch the MSI) so you can be more certain of which steps failed.
For instance, when you try to launch your executable, you can check the default download folder to see if the MSI file was downloaded there.
If it wasn't downloaded, the most probably this is an issue with the download process. If it was downloaded, the it might be a problem with the launch of the MSI file. For instance, if you are trying to install it silently, you will need to provide administrative privileges (the user must be an administrator), otherwise nothing will happen.
Hope this helps.