IMac Can’t connect to https servers

Is your Clock within a few seconds of correct?

Are you using a VPN?

Are you running in a Parental controlled Account?

Open Network Utility in Applications>Utilities>TraceRoute Tab, enter google.com & report what the output is, like...

Traceroute has started…

traceroute to google.com (172.217.14.206), 64 hops max, 72 byte packets

 1 192.168.43.1 (192.168.43.1) 2.274 ms 2.152 ms 1.964 ms

 2 10.198.22.177 (10.198.22.177) 36.855 ms 36.014 ms 39.991 ms

 3 10.170.233.106 (10.170.233.106) 32.850 ms 33.258 ms 38.967 ms

 4 10.170.233.101 (10.170.233.101) 33.056 ms 40.890 ms 43.815 ms

 5 10.164.176.237 (10.164.176.237) 31.952 ms 27.447 ms 39.148 ms

 6 pr02-ae12.sea09.net.google.com (206.81.80.69) 40.517 ms 47.185 ms 39.953 ms

 7 74.125.243.177 (74.125.243.177) 47.223 ms 47.613 ms 50.548 ms

 8 209.85.254.171 (209.85.254.171) 54.785 ms 42.696 ms 50.122 ms

 9 sea30s01-in-f14.1e100.net (172.217.14.206) 47.950 ms 48.018 ms 38.743 ms

Try this browser as a test...

https://brave.com/

By chance do you use any antivirus, cleaning or any other third party "maintenance" apps?

That is likely your problem! The best security and antivirus app for Mac OS is Mac OS itself! If simply kept up-to-date and otherwise left alone Mac OS will remain secure, stable and fast. Adding third party antivirus apps, cleaning apps and other types of "maintenance" apps have the exact opposite effect on Mac OS that you want, they make Mac OS slow, unstable and appear buggy.

Please locate the Avast uninstall instructions provided by their developers and uninstall. Then restart in Safe Mode and restart normally to re-test.

Your welcome.