*** first, front and center *** Do NOT confuse the code 16 error if you are modding downgraded versions of gtav with the information in this link. This link was created for code 16 errors pre-late march, april 2023 where downgraded versions throw code 16 after the launcher update.



There are a couple different things that can cause the code 16 ranging from permissions/lack of, antivirus, security, and some other.. trash. -.-

Start with this - verify you can infact log into your social club account on the website. Use Internet explorer - if it doesn't look right / only shows white/blue links carry on.
(dec2016 - for some- pages now appear proper - and "can" still be resolved from below)

Below steps are valid for Javascript callbacks and code -1002's in socialclub_launcher.log
and ----*****Mar/April 2016 - this also displays as an error code 16

1--------------------------
DOWNLOAD/save file - "Entrust Root Certification Authority - G2"
https://www.entrust.com/root-certificates/entrust_g2_ca.cer
or
https://web.entrust.com/root-certificates/entrust_g2_ca.cer
(The link works - if it doesn't for you - try a different browser)

Right-click entrust_g2_ca.cer and select Install Certificate. Pick ---
"Place all certificates in following store" and select "Trusted Root Certificate Authorities".
Run GTA. (might need a computer restart)
=================
In some cases- the above doesn't work and you can try adding the certificate here-
Right-click entrust_g2_ca.cer and select Install Certificate.
Pick "Place all certificates in following store" and...
Select "Third-Party Root Certificate Authorities".
Run GTA. (might need a computer restart)

=================
If you are a new user - or a brand new install/redone OS- (or just verify clean install)
I would also exit steam, rightclick steam, run steam as admin.
Open steam/steamapps/common/gtav/installers - rightclick socialclubsetup - run as admin.
(or manually download from R* Click Me! [patches.rockstargames.com] (sometimes outdated)
Try gtav again (after the cert install and computer restart).


2-------------------------------------------------------------
If the certificates are absolutely known to be installed properly... (ha ha -.-)
In a few cases - code 16's have also appeared from corrupt OS system files.
Running an admin command prompt and sfc /scannow fixed those.

I have yet to find a code 16 that was NOT fixed with the above instructions.
If it doesn't work for you - I suggest you double/triple check you did them correctly.
(or find someone who can - like me, teamviewer, over candlelight~)

3--------------------------------------------------------------
Due to the new launcher - and possibly mutating issues due to multiple errors conflicting with each other - it is also possible for other background apps, antivirus, security apps, and browsers to give you issues with this (especially chrome at the time of this post). Temp pause/sleep or disable (possibly even uninstall them temporarily) and try again. The new launcher also installs vcredist 2015-2019 and you may need to be doublecheck that has a clean/correct installation as well.

Edit - I should note - this is from 2015-2019+, and typically certificate errors. The (2020/21)new launcher/social club versions are also pop'n code 16's at a different location and not generally being repaired via the certificate. Most are seemingly repaired via sfc scannow, fixing/reinstalling vcredists, directx, and who knows what else. R* isn't known for giving singular problems singular errors. -.-

Incase you still have problems because the above "doesn't work" but the code 16 has disappeared - it has other assorted fixes for social club---
Big link of social club / connection related fixes - Click me~



**Additional note - Some steam users can download the link below - rightclick - run as admin.. Ignore the errors. Simply run it and done. YMMV here. Really only useful after whatever was initially preventing the certificate install is corrected/disabled in the first place -.-
http://patches.rockstargames.com/prod/gtav/Launcher_EFIGS/GTA_V_Launcher_1_0_1290_2.exe

** IF you are having problems viewing the social club website -
You can also try different browsers. Some might be more restrictive than others... -.-

** There have been a couple incidents now - where after this link, code 16 still appeared. It then resolved itself after a couple hours, or even minutes. Nothing else changed in a couple of them - that I know of. Leads me to believe there are now additional causes for this error that are not on the user end (like a couple other errors now). -.- Still needs more testing. --- months later, still unverified. Pretty sure certain end users were lying.

As already said - if this "doesn't work" - I can teamviewer and verify your work / fix myself.



Oriignal link - Social Club code 16 -
https://psteamcommunity.yuanyoumao.com/app/271590/discussions/0/152390014795429624/#c152390014795433872