I describe the solution in this tread: [URL]  It may also by an idea to run CCleaner to delete temp files and scan for register errors after you have uninstalled supportassist and the MS store version (if you have). Then preform a restart before installing supportassist again.    
Do I uninstall all 3, Dell Support Assist, Dell Support Assist Remediation, and Dell Support Assist Update Plug in, before trying the reinstallation link provided?  Alienware 15 R4 Intel(R) Core(TM) 8300H CPU @ 2.3GHz 64-bit Windows 10 Home Version 1803 Build 17134.112 [URL]  
SupportAssist Not Responding at Launch