Wifi constantly going down - Zyxel T56

Dear customer service,

Apologies for writing in Engels and writing in another thread on the same topic before without explaining the problem in detail. 

3 days ago we moved houses and transfered our internet Odido contract. The new house has optic fiber so we got a new modem - Zyxel T56 - which was setup by a Guidion technician. Not sure if the problem started on day 1 but for sure the second day our Wi-Fi started dropping constantly. If I reset the modem or do a powerflip I get Wi-Fi back for a few minutes and then it is gone again. If I manually try to connect to the network it tells me the password is incorrect (iOS). These are the solutions I found on other threads in this forum. I also read about a firmware update but the posts were older and apparently the router should update itself when first connected.

The problem seems to be with the Wi-Fi only since I have internet if I my laptop directly with the Ethernet cable. All the lights are green regardless of whether my mobile has Wi-Fi or not. 

@Tommie van Odido you mentioned in the other thread that you see devices connected to Wi-Fi. Occasionally we do get Wi-Fi on our phones but usually only after resetting and for brief periods. We do have a couple of home devices that connect to Wi-Fi but we were in the process of pairing them up with the new network when we encountered the Wi-Fi issue so I’m not sure any of them actually paired and are able to connect to the network when Wi-Fi is working. 
 

We actually called customer service that forwarded our problem to the technical department and if nothing can be solved like that a technician from Guidion will come by. Since I had already mentioned the issue here in the forum I decided to follow up anyway. In the end any help with be very appreciated!

best,

joao