Cannot Connect to App Store (Or iTunes)

I'm struggling to login to App store or iTunes. I found several posts on this issue already:

Cannot Connect to the App Store

macOS: Cannot connect to app store

Cannot connect App Store after upgrading to Mavericks

When I open my Mac and select apple menu > app store I see a blank grey square:

When I try to log in by clicking store menu > sign in I receive an error message "connection failed".

Then, when I try to open iTunes "The certificate for this server is invalid":

I followed the steps advised in several blog posts on this e.g. this one.

These steps include:

1. Verifying I have internet connection via network settings window
2. Set Macs DNS server to Googles with 8.8.8.8 and 8.8.4.4. Mine was set to this already. Restarted Mac. Problem persists.
3. In finder, navigated to /var/db/crls/ and moved both cricache.db and ocspcache.db to the trash and then emptied the trash. Restarted Mac, problem persists.
4. Looked for problem certificates in Keychain access under /Applications/Utilities/. "In the left pane, click on Certificates under Category. In the search field at the top right corner of the KeyChain Access window, type Class and press Return. Among the search results, locate and double-click on a certificate that has an icon with a blue outline. This will open a window with information pertaining to the certificate.". None of my certificates have a blue outline, everything appears in order here.

Other information: I don't know which version of Macos I have because when I navigate to the Apple menu > about this Mac all it says is Macbook OSX 10.9.5 (Mavericks?):

I have an ssd drive. I don't know if that's relevant or important.

Exhaisted all Google searches, blogs and posts. I would like to install any available updates, login to iTunes and generally just use my Apple ID with my Mac.

Does anyone have a solution to this or hypothesis about what I can try next?

EDIT:

Some new information. From a comment I visited https://init.itunes.apple.com in Safari and then selected show certificates which resulted in this screen shot:

Solution 1:

Your user profile on your Mac might be compromised.

To test, create new user and try to access iTunes or App Store.

If it works lets try repair your user profile with permissions repair.

Restoring the OSX from backup will not fix that, it will keep your user profile as is.

Just as safety and unexpected problems, create second Administrator (full access) account.

Launch Disk Utility, located at /Applications/Utilities/.
Select the 'First Aid' tab.
In the left-hand pane, select a volume you wish to run Repair Permissions on. ...
Click the 'Repair Disk Permissions' button.

Also see this article to restore/reset permissions

But your problem might be even deeper. The certificates reside in KeyChain.

Repairing keychain it might be tricky so follow the instructions carefully (like FIRST make BACKUP).