The hub3 sounds like needs replacing if it can't save any settings at all. Could be borked firmware update.
If your hub was off at the time then your IP address would probably be located elsewhere. To be honest I'm pretty surprised you know your iP address by heart so are you really sure it was your own.
Anyway it seems you account has been compromised so clearly you need to change your password to a secure one. However if your pc's have a virus infection this could be pointless as your password will be simply hoovered up again.
So check your pc equipment for virus's
Once you've sure your pc equipment is clean change your google password and make sure you don't use a simple one like your sons name or birthday. Log into gmail then check your online activity via the details link in gmail. That will tell you where you been logging in.
Under security check your what devices you have revoke any your don't recognize.
If you don't use third party mail clients disable make less secure apps isn't enabled.
Also check what apps you have installed on any mobile devices. Check online too see if you installed any dodgy ones.
It's unlikely the firmware has been hacked and I suspect it's more likely an easy password to guess or you've used your details on other forums and they've been hacked or a company you've been bought from online has been if you've careless with credentials. Or you've responded to a phishing email or let your little ones onto your computer and they've been naughty while you haven't been looking.
The IP address used was my external IP address the same one I'm on now. I use RainMeter software which shows my external IP address. Which is still the same one now as was when the hack was done and this IP address has been with my Hub3 since renewing my contract with VM coming up to a year.
The other day I put the Hub3 into modem mode and connected a different router (DD-WRT) which then gave me a new external IP address. Then reverting back to my old IP address when change out of modem mode.
As I have said I write code including network stuff which requires me to know my IP address, I also like to tinker see whats what and how things are setup disassemble code (IDA, X64dbg etc) I have tried The CIA`s Disassembler "Ghidra" a few times
All pswd's changed on day of hack All drives wiped (Gparted) and zero'd
I am 99.9% sure until I recieve a new Hub3 or I do not connect to VM's network for approx 21 days for the lease to expire and be allocated else where.
So to me, alternitive possibilties are Googles screw up or it's on VM's side.
My current IP address is the same as in these images and as I've already said it's all provable.