App Store Header icons missing

Get a complete and current backup, if you do not already have one.

Remove Clean My Mac.

Use the vendor’s instructions.

Given various other postings discussing issues with and discussing the removal of that and of similar cleaning tools, a (partial) reinstall of macOS may be required to remediate any remaining corruptions.

And by all appearances, you do have a corruption here.

Which means downloading High Sierra from the Mac App Store, and re-installing it here. Do not erase and reformat. That re-install is usually harmless to your files, but does reload the operating system and its files.

But again, do have that external backup. Or two. Your own data is the toughest to recover.

I think you'll have to Reinstall the OS since you can't get the App by itself.

Have you tried this?

To find out if it's system wide or user specific, try this...

Open System Preferences>Users & Groups, unlock the lock, click on the little plus icon, make a new admin account, log out & into the new account.

Does it work in the new account?

So to confirm, you logged out of the App Store, and back in again?

And you also tried the Mac App Store while in Safe Mode?

Create a new user on your Mac, log into that, and log into the Mac App Store there. See if that works better.

Any add-on anti-malware, anti-virus, optimizers, cleaners or network-firewall-and-filtering apps installed here?

Restoration? I wouldn’t be sure that other corruptions haven’t or didn’t start earlier than the overt corruption, for whatever caused this. It’d be nice if this were the only corruption and that no other latent corruptions existed, but that’s not certain. Add-on privileged software—anti-malware, anti-malware, cleaner apps—have full system access and variously don’t and/or can’t coordinate with macOS for whatever parts of macOS they’re modifying... And you probably don’t want to restore to prior to when the cleaner was installed and if that app was the cause here, because that could well have been a while ago and you’d lose your other updates and changes.

Here’s a direct link to download High Sierra: https://itunes.apple.com/us/app/macos-high-sierra/id1246284741?ls=1&mt=12

Or use a second Mac, download High Sierra there, and build a bootable installer. Transfer that to the problem Mac, and use that for a backup, and to reinstall without the erasure.

Again, have a complete backup first. This because the corruptions might necessitate a wipe and reinstallation and migrating in your files and apps from the backup.

Whew, most of my tools have a problem with http://www.techstream.net/, but my browser gets it???

Make a New Location, Using network locations in Mac OS X ...

http://support.apple.com/kb/HT2712


System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.

System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.

The interface that connects to the Internet should be dragged to the top of the list.


Instead of joining your Network from the list, click the WiFi icon at the top, and click join other network. Fill in everything as needed.

System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...

8.8.8.8

8.8.4.4

Apply.

Log out of the Mac App Store, reboot, log into the Mac App Store, and try again.

If that fails, log out of the Mac App Store again, reboot into Safe Mode, log into the Mac App Store, and try again.

EtreCheck is a simple little app to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac.

http://www.etresoft.com/etrecheck

Pastebin is a good place to paste the whole report...

https://pastebin.com/

Workable but harder for me to work with...the Note tool on the bottom of this editor's toolbar, as shown in the image, to copy and paste the output from EtreCheck.

There is also Malwarebytes...

https://www.malwarebytes.com/mac/

You don't have another Browser to test?

Open Network Utility>Traceroute tab, enter google.com, what does that report?

Traceroute has started…

traceroute to google.com (172.217.11.174), 64 hops max, 72 byte packets

1 192.168.43.1 (192.168.43.1) 1.675 ms 1.684 ms 2.125 ms

2 10.198.37.33 (10.198.37.33) 49.668 ms 55.172 ms 59.907 ms

3 10.0.115.1 (10.0.115.1) 60.066 ms 66.144 ms 59.960 ms

4 10.198.37.1 (10.198.37.1) 59.275 ms 56.150 ms 61.440 ms

5 10.165.50.210 (10.165.50.210) 58.583 ms 57.804 ms 66.578 ms

6 10.165.50.213 (10.165.50.213) 51.811 ms 53.633 ms 58.948 ms

7 10.164.176.225 (10.164.176.225) 61.155 ms 49.916 ms 60.416 ms

8 209.85.174.14 (209.85.174.14) 65.554 ms 62.227 ms 61.987 ms

9 108.170.247.129 (108.170.247.129) 57.838 ms 63.171 ms 60.289 ms

10 108.170.225.69 (108.170.225.69) 62.408 ms 83.941 ms 71.312 ms

11 lax28s15-in-f14.1e100.net (172.217.11.174) 57.040 ms 67.654 ms 51.928 ms

Clean My Mac has been known to cause assorted problems.

Whew, great to here Woody, good luck! :)

What you’ve shown looks like a captive Wi-Fi portal, or wireless network provider portal of some sort.

If this is effecting several local systems using the same ISP network connection, and if your ISP is reportedly working on upgrades, then this is almost certainly a problem with the network you’re connected to.

I suspect your ISP still has a few upgrade-related kinks to work out. Either with your ISP modem, or within the ISP network.