Yeah at home the dhcp gives a long enough time span that devices tend to keep same IP.
Mobile hotspot connecting pi to my phone for out n about use did similar, meaning I could setup quick remote access via juice ssh.
Suddenly if I reboot a pi connected to my phone 4g via hotspot it issues it a new ip address where only the 3rd number set is changed e.g 192.168.xx.yy becomes 192.168.zz.yy. This means I have to find the ip address in the connected device list, then update juice ssh, then accept a new verification key when I connect after each shutdown or reboot. This isn't as simple as I'd previously enjoyed.
I thought it might be to do with a recent Android upgrade on my phone but it's the same when using a different device.
I'll look into setting a static IP at the pi end of things as that'd help loads. Ta.