Stealth mode does not need proxifier to use the proxies
If you have the account already made then just add the account, add the proxy to osbot (When you launch osbot and have the option for Stealth/Mirror it also has a checkbox for proxy and + button to add new proxy
Try adding the proxy (With user:pass auth if it's required) (You might have IP Whiteliste if you don't have user:pass)
Then before selecting Stealth click the dropdown box for the proxies and select the ip and then press stealth and it will load the client on that proxy.
If the client fails to load OSbot then the proxy is likely HTTP(S) and is the wrong protocol , otherwise it will launch via the proxy
No blocks are required nor does proxifier need to be open for the proxy to be used via Stealth (Proxifier is only required for Mirror mode)