Check if you have an active network connection. Zoho Vault's offline mode only works when you're logged in to your account. If you have logged out from the browser extension, you will need an active internet connection to access your Zoho Vault data. 

If this doesn't help, contact your IT admin and have them add the following Zoho domains to your list of trusted domains: vault.zoho.com, vault.zoho.eu, vault.zoho.in, vault.zoho.com.cn, vault.zoho.com.au

This will prevent firewall restrictions from hindering your access to Zoho Vault’s domain and extension.