A factory reset should only take a couple of minutes at the most, and once the home hub reconnects to the Internet, you can go into the hub manager and disable smart setup.
Wireless devices should reconnect automatically. Then try your camera again to see if its any better.
I have reset the hub. Have done that before for some reason bt cannot remember why.
When it comes to smart set up the first page is asking me to get on line with smart set up///get started////so have I got smart set up in the first place?
Smart setup is activated by default, so you need to ignore that screen and simply go into the hub manager
From the help page. Its the same for the home hub 5.
Select No and then click apply.
You do not have to change it unless you really want to, as the home hub cannot be accessed anyway unless someone has that little card, or can read the information from the hub itself.
Why I suggested you turn smart setup off, as it can interfere with devices like cameras which do not have an inbuilt web browser.
Whether what I have suggested will help with the camera, its difficult to say, especially as you are having an issue with the app, but its worth a try.
If all else fails then I think there is a helpdesk number on the BT shop link I posted.
Also check the user guide https://shop.bt.com/content/uni2/documentation/dqn6/smart_home_cam_user_guide.pdf
It does sound more like an issue with the tablet as it may not work with the updated app.
I wanted to eliminate any possible issues with the home hub first, which is what you have done.
Hopefully the BT helpdesk can suggest a resolution, if the user manual does not have the answer.
There are a few threads on the forum which may help.