If you have upgraded to Studio One 4.5 and your plug-in scanner is hanging when launching the program, it is because you are offline. One solution to this issue would be to go online with your computer. If this is not an option, here is what you can do...
Go to Run in the Windows Start menu or open Cortana. Type in %appdata% and press enter. From the Roaming folder that appears, go into PreSonus/Studio One 4
From the Studio One 4 folder, go into x64 and locate the Vstplugins.settings file. Right-click the file and choose to open it with Notepad.
In the Vstplugins.settings file, locate the following line: <Attibutes scanAtStartup="1"> Change the 1 to a zero and save the file.
This workaround will prevent Studio One from scanning plug-ins on launch and should resolve your issue. Previously scanned plug-ins will still load. Another option is to install the 4.1.4 build of Studio One and go into Studio One>Options>Locations>VST Plug-ins. From here, you can un-check the "scan at startup" option. You can then install Studio one 4.5 after doing this, to get around the problem.
If you would like to roll back to a previous build, you can. Just log into your my.presonus.com and go to My Products>Software>Studio One 4. There is a link to view previous versions. You can download 4.1.4 from this list. Just uninstall version 4.5 and install version 4.1.4. Please check future release notes to see if the issue has been resolved.