Ever since I started using api 26 as my targetSDKVersion, it appears that older versions of Android (Generally 5 and down) can no longer make calls to my server. I don't have an older device to test on, but these are reports that are coming in from users. My minSDKVersion is set to 4. I use the okhttp libraries for the calls, but the switch from http to okhttp was possibly done haphazardly, so I'm not sure if something is clashing somewhere. Does anyone have any idea of what could be causing the problem?