HOW DO I DISABLE SIP ALG FUNCTIONALITY IN M5?

I'm Trying to set up Voiply’s adapter so I can use my cordless landline phone to make calls via the internet (VOIP)

Connection sequence: Arris/Motorola SB6121 modem-> M5 in Router Mode ->TP-link 5-Port switch->Voiply adapter

RESULT: Internet access to desktop and laptops works great. The Voiply adapter has been assigned an IP address (192.168.68.110).

Problem: Adapter is not registering properly.

I'm told I need to disable "SIP ALG" ( Session Initiation Protocol and Application Layer Gateway respectively) settings.

Purportedly as easy as entering the Advanced Features area of my router SW and disabling "SIP ALG".

I have been unable to locate such a feature.

This address 192.168.68.250, after log in, only offers log and firmware update options

How can I accomplish task please??