I have two Mac user's that cannot run client version 18. I have installed the client from both the App Store and a direct download from Parallels website. The client will install and load properly. Once the user opens the Desktop the whole screen turns red. If I downgrade the client back to version 17 the users can see Desktop as normal. I have turned off graphics acceleration and set the colors to 256. Neither change helped. Any idea what could be causing this behavior? I have a few other Mac clients that have no issue. I have seen no issues with Windows clients. I do know that one of these users is running MacOS 10.12.6 on a Mid 2011 iMac. This is a supported OS version according to documentation.