I am having a similar issue.
When I first set it up, everything was great and it was working fine, no problems apart from battery changes. Had invited family members and it was working remotely for them too.
However, my phone broke and I needed to replace it. In the interim, I factory reset the bridge & the nuki and paired it with an old phone, sent the invites to my family members of which, it was working again.
However, when I am remote, it shows as offline, when close or within proximity and our phones are connected to the wifi and/or to the Nuki via bluetooth, the Nuki works. It does not work however via data/remotely.
I have tried factory resetting multiple times to no avail and similar to Nicola Reina above, this is a real pain. Up until now I thought the Nuki was the best thing ever but if I can’t get this fixed or if the problem persists, it’s going to be a major issue for me.
Even worse is that I am on the road a lot and can not be present to troubleshoot and need one of my family members to do it.
I have tested being connected to the wifi/bluetooth/data only and it works via wifi only, bluetooth only (& both wifi or bluetooth) but not data.
So everything is connected and working but only within proximity, no longer remotely as before?
What could the issue then be?