Thank you for contacting Presonus Technical Support. Sorry to hear about the recent issues you have been experiencing.
Make sure you are downloading the VST add-on with Google Chrome. Re-download the VST Add-on with Chrome.
Delete the current VST Add-on and reinstall the Add-on.
1. With Studio One open, go to Help > Open Settings Folder. Leave this folder, open but close Studio One.
2. Inside this folder is a folder called Extensions. Inside the Extensions folder you should see the Plug-In Support folder. Delete this folder.
3. Reopen Studio One. After you do this, drag the newest downloaded VST add-on on top of the window to install. Then Activate.
If the issue remains, please create a ticket to technical support.
Here is a link to create a ticket: http://support.presonus.com/hc/en-us/requests/new