Re setting my Netatmo Thermostat as its not connecting to the server.

I had a new Worcester Greenstar Ri boiler installed in May 2015 and they took my old manual Honeywell thermostat away and replaced it with a Netatmo S+HARK Thermostat, the engineer did all the setting up on my Smartphone and it worked fine, turning it on and off when I was away from home, until I changed my Broadband provider from PlusNet to EE a few weeks later and had to let my new EE WiFi router find my other things like the TV, the printer which it did but when I tried to find my Netatmo thermostat I got a message saying it couldn't then connect to the server, it kept saying cant find the server no matter what I tried, so have had to use the thermostat manually ever since by pressing up and down to adjust room temperature, but lately it switches itself off at various times in the day and at night and in the mornings it is still off and I have a cold house. I have tried communicating with the helplines back in 2015 when it started doing this cant connect thing but I never understood the directions I was emailed. They have no phone helpline! Please could someone quote what it would cost to send an electrician to connect my thermostat back to the wifi? Thank you. I'm a pensioner so I don't really understand their instructions and the technology. I have no idea what the password was as the engineer set it up. I lost all the App off the smartphone when it was hacked and was reset to factory settings so have managed to reload the Netatmo App back on yesterday. Thank you.