I think I have the answer. A while back at the summer cabin the adsl was shut down and I bought a 4G router and sim. While being on wifi I could watch, while being on 4G I could not.
Turns out packets with ipv4 are cut off and ipv6 is needed for eufy. Isp made sure I had ipv6 and set that up in the router aswell but same issue.
Bought a more expensive 4G router and it worked out of the box.
I have email conversations mile long with eufy support regarding this. Why did my wyze, arlo, reolink and blink cameras work on that cheap router that cut of the packets between router and eufy homebase but not they eufy 2C. Guess their packets are longer? Its for sure a eufy feature.
Heard people needed to get their isp to make sure they get ipv6 home and activate that in their routers and some, like me that also needed a better router.
Heres more Unable to connect to Homebase (-3)