AirCard 797 Mobile Hotspot

Dear all, I have bought an Aircard 797 with a LTE sim for setting up a remote mesuring system and accessing trough the web. The instrument is a Fluke 1748(power meter) who is connected to the hot spot WI-FI.

The application software from Fluke is installed on a PC, when the PC is connected to the same wi-fi everithing works fine.

We set-up the port forwarding as recommended by the instrument manufacturer, then we read the public address of the hot spot with a web utility like myip.com

The next step is connecting the PC to the instrument via the mobile hot spot from office trough the web, we know the public address of the router but wen we start the PC application we cannot reach the instrumet.

some additional information:

The SIM card inside the hotspot has a varaible IP address, everytime we reset or cycle power a new address is acquired by the hotspot.

When we chech in the information page of the mobile hot spot we see a diffent IP address than we see using myip.com, and is not clear to me the reason.

We have tested both address but none is working.

The mobile hot spot is not anwsering to a ping on either IP adresses.

Just fo more information we have done the same set-up on and home router connected with ADSL copper wired line and we can access from outside the router and the instrument, so we are quite sure the instrument and router parameters ( port forwarding) are correct.

Thank you in adcance to anyone who can help me in solving this problem.