Hi there.
I have had the current iPhone app on my iPhone for some time ( 3 months) and it works fine, no issues at all.
I'm not aware of any more recent version of the App
Which OS version is your iPhone using? If it;'s higher than iOS 12 then you should be OK . Mine is running iOS 14.4.1.
if you are running a lower version of iOS then the Brennas iPhone App might not work.
There is a possibility that one of the devices you are using isn't connected to your own router.
This could be
a) your computer
b) your iPhone
c) your B2
YOu said all your devices are connected to the internet , but are you sure your iPhone is connected to your WiFi? If it isn't and is using mobile data then you will not be able to connect to the B2.
How to check
1) Using your computer connect to the log in page of your router via a web browser on your computer. It should have an address such as 192.168.x.abc ( where the letters are variable. All the devices you are using should be using an IP address begining 192.168.x If you don't know the router IP address then you will find it either on the router case or in its documentation .
2) Log in to the router via a computer browser using the log in details with the user name and password provide in the documentation
3) Most routers will have an area where you can see a full list of all connected devices .
If your iPhone and B2 are connected to your router they will be listed. Most routers will allow you to fix (or reserve) an IP address for a particular device, such as the B2. This means it won't vary and will be easy to locate from a browser or iPhone App.
Persoanlly I think that your iPhone may have become discnnected from your router and is using mobile data, or, your router WiFi signal is weak and the B2 is not making a solid connection, perhaps it is located too far away from the router?
Anyway, good luck