Class style Teams channel links not opening

HelloMmcdan810 

welcome to the Microsoft community, my name is Recep I'll be happy to help you today.

I understand that Content links on your Home page to linked files in teams are no longer working by simply clicking on them.  Here are a few suggestions you can try. 

1. Update MS Teams: Make sure you are using the latest version of the MS Teams application. Check for any available updates and install them if necessary. Sometimes, outdated software can cause compatibility issues.

2. Check browser settings: Verify that your default browser is set correctly on your computer. MS Teams may rely on the default browser settings to open links. Ensure that the default browser is set to a compatible and up-to-date browser.

3. Clear cache and cookies: Even though you mentioned that you have already tried clearing the cache, it's worth attempting again. Clear the cache and cookies of both the MS Teams application and your default web browser. Restart the application afterward and check if the issue persists.

4. Disable browser extensions: If you have any browser extensions or add-ons installed, they could potentially interfere with the link opening functionality in MS Teams. Temporarily disable or remove any extensions related to browsers you are using and see if that resolves the problem.

5. Try a different computer/user account: Test opening the links on a different computer or user account within your organization. This will help determine if the issue is specific to your computer or account, or if it's a more widespread problem affecting multiple users.

6. Verify network settings: Ensure that your network settings, including proxy settings or firewalls, are not blocking MS Teams from opening links. Contact your IT department or network administrator to confirm if any network configurations could be causing the problem.

7. Restart computer and network equipment: Sometimes, a simple restart can resolve temporary glitches or network-related issues. Restart your computer and any network equipment (routers, switches, etc.) that you have access to, and then try opening the links again.

Also note that Server 2016 is out of maintenance support, there will be no fix. 
The issue is related to maximum character URL-limitation by OS.
Two possible workarounds:

• update to Server 2019
• disable SafeLinks Policy in Security AdminCenter (including exeption for BuiltIn-default-policy) and wait 24h

The issue propagates through all tenants starting about a year ago... so some organizations are affected for quite some time and some only recently.