iMac connects to Ethernet/WIFI but no internet connection

I am by no means a tech wiz and I barely know my way around MacOS so I’m hoping someone else may have come across this problem.

This issue started happening a couple days ago on my iMac. I am not able to load any websites in Safari.

It keeps giving me the “Safari can’t open the page because Safari can’t find the server.” error.

I googled the issue and one suggestion was to delete/forget the WiFi network and then fully shut down and reboot.

Deleted WiFi connection and shut down the iMac and rebooted and I reconnected the WiFi successfully but problem still happening.

I successfully connected Ethernet and this did not solve it either.

I know I’m not running the most up to date version of macOS:

so I attempted to update and it can’t find the server in order to do the update.

So, when I go through the process of connecting WiFi I get a notification on my iPhone to share the password and I tap the share button and this error pops up:

Also, I was able to successfully print to a WiFi printer connected to my WiFi network.

So, I think the iMac is successfully connecting to my local network and is able to see and discover other devices but for some reason cannot connect to the internet.

I have quite a few other devices on my network: other computers, smartphones, consoles, streaming boxes, etc. all of which have no issues.

I rebooted my router and this did not fix the issue either.

I am not running any VPN’s on the iMac.

I don’t have any other browsers other than Safari.

Appstore isn’t working.

I’m pretty stumped with this one and any help/suggestions would be much appreciated. Thanks in advance and let me know if there is any other info I can provide that would be useful.

[Edited by Moderator]