Espresence not working with iphone 11

i was able to get ipad air 2 working with Espresence bluetooth using this method Apple | ESPresense
strangely, it does not work with iPhone 11. the phone can easily see the “Espresence” bluetooth device. when i click on Espresence, the iphone looks like it’s trying to pair but ultimately fails as seen here:

any idea why pairing failed even though it was 18 feet away?

This is not the espresence forum.

Try restarting the board or pushing the enroll button again. If that doesn’t work visit the board via the browser but add /ui after the ip address. Give the device a name, add it, try pairing again.