Cant access internet homebase 2

So, in the summer house I have homebase 2 and 4 eufy cam 2c. Works like a charm.

Internet provider has decided not to provide internet as they used to so they sent a zte 4G modem/router and simcard.

It got 4 eth ports and all smarthubs, alarm system etc works but the homebase 2 sais ”cant connect to internet” or something similar. Connecting homebase 2 to the 4g routers wifi works but it still cant access internet.

Wird thing is I can access eufy from the app and stream the cameras but cant change any settings like away / disarm or change name. Then I get ”cant connect to homebase -3”.

Since all other devices work and eufy does not its either homebase 2 doing weird sh*t trying to access internet or the zte 4G router being just crappy. There are no firewall options logged into that router.

Bought a new 4G router and when it arrives I will know but have anyone here any experience or ideas of what the problem can be?

As soon as I connect it to old still working modem/router it works perfect.

Eufy support came back to me and said -3 error means unstable network. Still seams odd I can stream all cameras no problem ans watch saved recordings but not change any settings (sensitivity, name, modes) using this router. If anyone has any tips or tricks please let me know.