Have you looked at post @anonymous_user_1da90bc6 made and tried what link suggests? Please let us know if that also does not help and we will be happy to further assist.
“We have found a correlation between this and another issue, where solution generally works for both. Please follow link to other post and try solutions recommend there: [Official] Read this if your Download has stopped around 81% - Getting Started & Setup - Epic Developer Community Forums”