What i mean is, this service doesn’t sound like it’s a VPN at all. More like a software firewall that blocks or allows access to certain domains.
If it’s not easy to figure out on your own with whitelist rules, then I agree with @Mavrrick58 that you’ll need more info from support at this company, and maybe ST support too, in order to figure out how to whitelist what’s being blocked.
It’s probably worth pointing out that installing the ST app on your kids’ phones has some potentially huge downsides, since ST does not allow for any configuration of user permissions.
Basically you’ll have to accept the possibility that your kids could wipe out your entire ST setup if you install the mobile app on their phones. Yes that would be an extreme case, but they could end up messing something up in any number of ways, either inadvertently or intentionally.
If your goal is to use their phones as mobile presence sensors, consider installing the Life360 app on their phones. There’s an integration with ST so that the phones can still be used as presence sensors within ST, no need to have the ST mobile app installed on their phones.