Appium Studio always recommended paid account as free account had its own limitation even before.
If Apple has added something recently, even some other user complained , Appium Studio cannot do much about it
See the log below when we use Free account, the log indeed shows that its from Apple;s classes (not related to experitest related classes which is generally com.experitest.)
Server says: Please update to Xcode 7.3 or later to continue developing with your Apple ID. (3018).
at xign.client.entity.AppleServiceResponse.putRawResponse(AppleServiceResponse.java:49)
at xign.client.AppleDeveloperPortalClient.extractAppleServiceResponse(AppleDeveloperPortalClient.java:538)
at xign.client.AppleDeveloperPortalClient.sendRequest(AppleDeveloperPortalClient.java:448)
at xign.client.AppleDeveloperPortalClient.sendRequest(AppleDeveloperPortalClient.java:336)
at xign.client.entity.certificate.XCCertificateProvider.submitDevelopmentCSR(XCCertificateProvider.java:72)
at xign.client.entity.certificate.XCCertificateProvider.submitDevelopmentCSR(XCCertificateProvider.java:62)
at com.experitest.device.ios.profile.devportal.DevPortalController.submitDevelopmentCSR(DevPortalController.java:260)