NTP is being blocked somewhere. See if setting the router IP as the NTP server works, some routers will give a response to requests.
I tried this yesterday. First timeserver pool.ntp.org second 192.168.0.1 (router) - it was still not working.
In the meantime I solved the problem after the hint from elonesna. First I laught about this ordinary hint, but then I tried it again.
So I reboot the whole router. After the second reboot it works! After several hours of anger and a hammer lying next to the pi, waiting for its use - ITS WORKING...
Thank you to everyone!
For others who have this Problem, I put the whole problemsolving I found in the last hours in this document
try this solving steps - step by step:
1) activate "wait for network before starting kodi"
2) restart kodi
3) restart the Router 
4) try if kodi works with your smartphone tethering or another network! If it works your router have a problem!
Try number 2, Check in your router setting if libreelec ist connected, try to disable the firewall, make a ping from your router to the device to check if the device is there. Go to the libreelec connection settings - edit your active connection - ipv4 manual - check your dns and default gateway!
5) set the timeserver to pool.ntp.org
6) if this not work go to libreelec setting - Connections - select the network and go to edit - put IPv4 to manual - select time servers and put first time server pool.ntp.org and maybe the second to your router ip - and then change ipv4 to dhcp or just let it manual
7) use ssh - you have to activate it in codi - for win 10 use the program putty - open the program - to connect just write the device name - a terminal will open - the default username is root and then write your selected password - try to ping your router and try to ping the repositroy server. If this works and your time is still wrong and the repository still cannot be started I think you should try to set your router to default.
8 ) look for new versions of libreelec and try to do a clean reinstall
9) If it still not works - sell your pi and find something better in your life! =P