Though It should work. But for quick troubleshooting, you need to manually add the key for the second user as the same way it's added for your Admin account. To do so please follow these steps:
Run the registry editor (Hold Windows Key and R, then type in regedit)and navigate to the location Computer\HKEY_CURRENT_USER\Software\Mozilla
Select Mozilla Folder --> Right click on it --> Select New --> Key --> Name that new key as NativeMessagingHosts.
Now Right click on NativeMessagingHosts Folder --> Select New --> Key --> Named it as EnpassNMHost.
Double click on EnpassNMHost --> Double click on Default --> Set the same path as Admin account in the value data field.