MacBook Air connects to wifi but does not load webpages etc

For the life of me I cannot resolve this issue. I was given a 2013 MacBook Air and upgraded it to Big Sur on works wifi.

At home it will connect only to the 5ghz network (will not connect to 2.4 days incorrect password even though it’s correct). Once connected it shows the green dot and connected IP, however no webpages will resolve.

I’ve spent hours trying things online such as;

1. Restarting router/modem
2. Deleting system configuration files in the preferences library
3. Changing network options under the network pretences for DNS
4. Forgetting the network and re-adding it
5. Starting in safe mode - problems still persists
6. Clearing DNS cache via terminal
7. Adding “new” locations
8. Making sure time/date/region settings are correct
9. Turn off firewalls and removing anti virus software
10. Checking router blacklist & settings

I do not know where to go from here, the laptop works on other connections as well as my phone hotspot.

Most errors in the browser window are DNS_PROBE_... NO INTERNET

When I checked my dns via terminal there is 7 resolvers all not reachable and at the bottom under (for scoped queries) Reachable (8.8.8.8)

I have fiddled around with so many different “fixes” online and nothing has worked.

Any advice would be highly appreciated