Check the system date. When its not close to the present, the server will not connect*.
- Open Terminal: “utilities” > terminal
- type “date” in the bash display, it wil display the current set system date. Mine was 1/1/x (don’t remember the set year) – because the battery was serviced and got disconnected.
- set the date with “date 0426172718” to set the date to april (04) 26, and the time to 17 hours, 27 minutes and the year 18 for 2018
- close terminal
- run install
(*) However it’s also very likely that you forgot that the wifi is not set yet… luckily you get a very good descriptive error message /s