I also have this issue since upgrade to Parallels 17 - black screen on iPad with timer. I have tried reinstallation of Parallels and Access, checked permissions for screen recording and reset the permissions in Terminal. I have a ticket in with Parallels support, but so far the agents are all providing the same answer and suggestions to no avail. I am pretty sure its a permission issue, but I can't find where it is, its not the Mac Firewall or Privacy settings for access. Any suggestions?