Response from engineers:
We have received reports that iOS users are experiencing issues while initially launching the D-Link defend app for the McAfee-powered routers using the D-Link Wi-Fi app v1.2.7. We have found the root cause and are now working on a fix to rectify the problem. A newer version of D-Link Wi-Fi app v1.2.8 will be available for download from the App Store on June 15th, 2020