There are a lot of firewall errors 
out there. Way too many, right?

Quick fix

After being idle or off the 900 Firmware's error is indicated when the printer starts printing.

The 900 error only appears when the printer is receiving information from a computer or network. Contact your local helpdesk or software/network support first. This is due to a communication problem with the software or your network.

However, if the error occurs when the printer is idle or not connected to the network or PC, there might be a hardware or connection problem. Sometimes a bad connection with an internal network adapter/card can cause this issue

Best solution:

http://support.lexmark.com/index?page=content&locale=en&modifiedDate=10%25252525252525252F03%25252525252525252F12&actp=LIST_RECENT&userlocale=EN_US&id=HO3643

More solutions:

http://support.lexmark.com/index?page=content&id=SO5445&segment=SUPPORT&productCode=LEXMARK_C544&locale=EN&userlocale=EN_US

Quick fix

The Spotify error code usually occurs when users attempt to log in to their account. You enter your email address and password to log in to Spotify and it fails with the following error code:

A firewall may be blocking Spotify. Please update your firewall to allow Spotify. Additionally, you could try changing the currently used proxy settings (Error Code: 17).

The error message is self-explanatory and indicates that something is wrong with the used proxy settings.

Best solution:

http://techdescribed.com/fix-spotify-error-code-17/

More solutions:

https://www.anysoftwaretools.com/how-to-fix-spotify-firewall-error/

https://www.thetechtoys.com/fix-spotify-error-code-17/

Quick fix

When you try to start the Windows Firewall service on a Windows XP Service Pack 2 computer, you may receive the following error message:

Could not start the Windows Firewall/Internet Connection Sharing (ICS) service on Local Computer.
Error 1068: The dependency service or group failed to start.

Best solution:

https://www.auslogics.com/en/articles/how-to-fix-error-1068-the-dependency-service-or-group-failed-to-start/

More solutions:

https://www.how2fixerror.com/3-guaranteed-ways-fix-error-1068-dependency-service-group-failed-start/

https://www.thewindowsclub.com/windows-firewall-service-does-not-start

Quick fix

Error message 0x80070422 in Windows 8 appears in most cases when the user attempts to activate Windows Firewall. The reasons why the user receives this message may be due to a variety of malware or virus infections on a Windows device and may end up with some necessary Windows 8 or Windows 8.1 updates that the user has not previously made.

Futhermore, a disabled Background Intelligent Transfer Service (BITS) can also cause this problem. Background Intelligent Transfer Service must be in its working state.

Best solution:

https://windowsreport.com/error-0x80070422-firewall-settings-windows/

More solutions:

https://troubleshooter.xyz/wiki/fix-cant-turn-on-windows-firewall-error-code-0x80070422/

Quick fix

Firewall-cmd is a command line frontend for firewalld (firewall daemon), a dynamic firewall management tool with D-Bus interface.

It supports IPv4 and IPv6. Additionally, Firewall-cmd supports firewall bridges, zones and ipsets as well. It allows scheduled firewall rules in zones, logs rejected packets, automatically loads kernel modules, and much more.

If a syntax error occurs during execution of the command, the error can occur as follows:

# firewall-cmd -state
usage: see firewall-cmd man page
firewall-cmd: error: unrecognized arguments: -state
# firewall -cmd --state
-bash: firewall: command not found

Best solution:

https://www.thegeekdiary.com/bash-firewall-command-not-found-how-to-resolve-in-centos-rhel-7/

More solutions:

https://www.tecmint.com/fix-firewall-cmd-command-not-found-error/

Quick fix

Some old-school players have encountered the problem with the login error on the PC.  Messages, such as OSRS error loading your profile and Please contact customer service, appear, when trying to log into the game. This problem can happen on both Mac and Windows clients.

Hint:

You could try solving this login problem with the following possible solutions:

1. This problem can occur when the Internet connection is not strong enough to run the game. Make sure your Internet works normally.
2. Test your router. Unplug the router for 1 minute, plug it back in and wait for all lights to turn green. Sometimes there may be an ISP problem, so you need to call your ISP to gain further information.
3. Uninstall older versions of Java & OSRS Client and install the latest version.
4. Turn off all/any firewalls or disable them. Then retry it.
5. Restart your computer. Sometimes you may need to completely recover your computer.

Best solution:

https://www.rsorder.com/news/learn-solutions-to-osrs-error-loading-your-profile-login-issue

http://oldschool44.runescape.com/jav_config.ws?userFlow=2346410208033476580

Quick fix

Users who encountered the 6d9 error reported that their Windows firewall was involuntarily turned off during the installation of their security software. They also complain that they don't have access to the Internet. If you have the same problem, your operating system would most likely provides an APIPA IP address. You will receive an error message like the one below:

There was an error opening the Windows Firewall with Advanced Security snap-in, The Windows Firewall with Advanced Security snap-in failed to load, Restart the Windows Firewall service on the computer that you are managing, Error 0x6D9.

Best solution:

https://www.auslogics.com/en/articles/how-to-resolve-0x6d9-windows-firewall-error/

More solutions:

https://answers.microsoft.com/en-us/windows/forum/windows_vista-security/trying-to-turn-on-windows-firewall-getting-error/a8dc26c1-010d-4f16-8531-d609731f7015

Quick fix

Fortnite is one of the biggest online games of our time. With over 125 million users since its introduction on multiple platforms, bugs develop from time to time.

If you have problems playing Fortnite or cannot connect to Battle Royale, you should check the servers first. While the search for possible end user problems is fine, most connection problems occur within the game's servers. A common reason for connection problems issues is a scheduled downtime due to updates. Maintenance and planned outages, though not as common, are sometimes communicated by the publisher or developer in advance. Below you can find ways to check if there is a problem with Fortnite servers.

Best solution:

https://pcgamehaven.com/common-fortnite-problems-and-how-to-fix-them/

More solutions:

https://thedroidguy.com/2019/08/how-to-fix-fortnite-lag-issue-and-other-connection-problems-1097421

https://www.gottabemobile.com/fortnite-problems-how-to-fix-them/