When you login into the Secure/Normal mode WhatsApp, it assumes that you have got a new phone which yo are trying to activate and when you continue to register using the secure mode it unregisters Normal mode phone and vice versa.
When you login into the Secure/Normal mode WhatsApp, it assumes that you have got a new phone which yo are trying to activate and when you continue to register using the secure mode it unregisters Normal mode phone and vice versa.