Are you able to browse to the failed to access URLs?
Yes
If you can, then try and ping github.com, just to make sure you can reach it VIA the terminal.
ping -c 5 github.com
PING github.com (140.82.114.3) 56(84) bytes of data.
64 bytes from github.com (140.82.114.3): icmp_seq=1 ttl=45 time=279 ms
64 bytes from github.com (140.82.114.3): icmp_seq=2 ttl=45 time=323 ms
64 bytes from github.com (140.82.114.3): icmp_seq=3 ttl=45 time=365 ms
64 bytes from github.com (140.82.114.3): icmp_seq=4 ttl=45 time=304 ms
64 bytes from github.com (140.82.114.3): icmp_seq=5 ttl=45 time=348 ms
--- github.com ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4005ms
rtt min/avg/max/mdev = 279.308/323.821/365.324/30.523 ms