Please answer ALL of the following [admittedly tedious] diagnostic questions by number, preferably without quoting my post:

1a. When (approx. date) did you purchase the computer?

1b. Does the computer-in-question belong to you or to your son?

1c. Does your son's User Account have Administrative privileges?

1d. Has the Guest Account been disabled?

2. Did the computer come with Win10 preinstalled, did you do a clean install of Win10, or did you upgrade a Win7 computer or a Win8.1 computer [<=PICK ONE!] to Win10?

3. Who manufactured the computer (e.g., Dell; HP; Acer; Lenovo; ASUS)?

4. Has a Norton application or a McAfee application EVER been installed on the computer since you bought it?

5. Have you ever run the Norton Removal Tool and/or the McAfee Consumer Products Removal Tool?

6. What Version & OS Build of Windows 10 is currently installed?

• Press & hold the Windows Key and press the R key. In the RUN dialog, type WINVER and press the Enter key.

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Marking one or more of my replies as ANSWER at any point will officially close (end) your thread, whether your problems have been resolved or not. HELPFUL votes very much appreciated at anytime. Thank you.

Can you access your Microsoft Familiy account and does it appear to work correctly? https://support.microsoft.com/en-us/help/10551/...

Using a Standard account a user should not be able to access to change any System files or features without needing to insert the Admin password, so you might want to change that and not give it out to anyone.

Check over your system files to see if any are missing or damaged and replace them using the steps for that from this checklist: http://answers.microsoft.com/en-us/windows/wiki...

As you have time I'd also complete the other steps because they will assure the quality of your install which is what's most important in Windows 10, optimize your install for best performance, and do any needed repairs.

I hope this helps. Feel free to ask back any questions and let us know how it goes. I'll keep working with you until this is resolved.

Yes, you can try repairing your windows installation by running the SFC and DISM commands as described in this article;
https://www.howtogeek.com/222532/how-to-repair-...

The Pc is about 4 years old 

The Pc belongs to my son

My sons has admin privileges on the PC

Guest Account is running

It came with windows 10

Cyberpower 

Norton was not installed

Version 1709 OS 16299.19

How old is your son?

16 and a half

CSI    00001af0 [SR] Cannot repair member file [l:10]'WpcMon.exe' of Microsoft-Windows-ParentalControlsMonitor, version 10.0.16299.15, arch amd64, nonSxS, pkt {l:8 b:31bf3856ad364e35} in the store, file is missing

Which command gave you that error?

Long story, short version: If you don't want your 16½ year old son to be able to make such changes to the computer - even thought the computer belongs to him, you son should not have Administrative privileges.

Your User Account, on the other hand, should have Administrative privileges.

IMHO a 16½ year old should not have unsupervised access to a computer which has access to the internet - yes, even with Family Safety/Parental Controls enabled. The computer should be located in a common area of your home but not in your son's bedroom.

Here's some additional information for you:

Keep your kids safe in Windows 10
https://www.cnet.com/how-to/keep-your-kids-safe...

How to Setup Family Safety in Windows 10:
https://www.groovypost.com/howto/setup-family-s...

How to Add and Monitor a Child’s Account in Windows 10:
https://www.howtogeek.com/225323/how-to-add-and...

PS: Chances are your 16½ year old son knows way more about computers & parental controls than you or me. Good luck!