if its an issue with sprint only while trying to use that specific app..their developers would be the ones that need to contact Sprint and get it figured out..not vice versa..
Mint is more than an app they have a website to but you are blocking there ip address and by the sounds of it you don’t even know what mint is. Mint a a budgeting app. Look it up
I use Mint regularly and I am signed in without issue. Granted, I've been on quarantine since March 12 and always connected to Wifi, so I just turned off Wifi and it logged right in. My only guess is it's IPv4 vs IPv6. Sprint is moving to IPv6 only and if the app does only IPv4, it's going to have some problems. Like @fireguy_6364 mentioned earlier, that would require action from the developer. You can submit feedback to them at email@example.com