R6400 Connection Issue

Hello. I have a R6400 router that works just great with one new and frustrating exception. I have a swimming pool that has a Goldline Aqualink device. This device, previously, allowed me to access the pool from any internet connection and montor and change temperatures, filtration status, heater status etc. It worked flawlessly for several years.

Several months ago the Aqualink sign in page (http://www.aquaconnectweb.com) after signing in yields a "lost link" error message. I have worked extesively with Goldline Controls (the Manufacturer) attempting to solve the issue without success. The latest troubleshooting sessions just informs them to direct me to contact a network professional. I am reasonably tech savy but not nearly a professional.

The Aqualink device connects directly to my R6400 via an ethernet cable. The pool equipment controller has an RF device to transmit to/from the Aqualink device. The device does receive and send the RF signals properly to/from the pool. I know this because I am able to connect to the Aqualink device over LAN. This allows me to control the system over LAN turning on heaters, checking temperature, lighting and all other controls of the pool.

I was previously able to do this over WAN using http://www.aquaconnectweb.com but can no longer do so. I am quite frustrated by this and can not fix it. I have many other devices within my smart home that I can connect to and control over WAN properly.

The "lost link" did not conincide at all with any additions or removal to the network nor updates to the network or router software.

I know this because the home where this device is located is a winter home and the problem occured when I was 1000 miles away so I did not make any changes.

I am offering my spot in he que for a COVID 19 vaccination shot to anyone who can help me fix this issue.

Happy New  Year,

Tom