Untrusted certificate for a government official website

Hi Shawn.
Have you been able to address my comments above ?
Thanks a lot for your help
Bets regards
kevin

Hi Kevin,

We request you to reach the support of the website and inquire the reason behind this.
If not, you can post this on respective browser support page and ask them the reason.
You can also check whether the website is working on Internet Explorer.
Thank you.

Good Day.
connection to the official French Tax website https://cfspart.impots.gouv.fr (IRS-equivalent) is not authorized by any of my browsers (Firefox 78.10.0esr / Chrome 90.0.4430.85) although these browser versions are said to be supported by the governmental Tax website.
Error code: SEC_ERROR_UNKNOWN_ISSUER
Issuer Name. Common Name: AVG untrusted CA
Can anyone help on this one ?
Thanks a lot in advance
best

Hi Kevin. Thank you for writing back, and unfortunate this disruption persists.

Having used both a Mac and a PC, with AVG Internet Security installed, I am able to access the site without disruption. In other words, I am not able to replicate your experienced disruption.

Is this the only site, you are experiencing such a disruption when visiting, and are able to access other sites, without disruption?

Shooting from the hip, some additional troubleshooting: ensure your computer is fully updated, clear your browser cache and cookies, and to try opening the site in a incognito/private browser. Are you using any other privacy software, i.e. a VPN, and to ensure said privacy products are disabled. 

Let me know how this works for you. Regards, Shawn

Hi Shawn
Yes this is the only website that appears blocked. Cache, cookies, history are cleared on all three browsers used (Firefox, Chrome, safari). I tried with my VPN active or inactive, in private or non-private windows: doesn't change anything.

Only if I uninstall AVG, can I access the Tax website of the French government: https://cfspart.impots.gouv.fr
The website certificate is recognized as valid. In the absence of AVG (uninstalled), It is delivered by the following Certificate issuer (Sectigo Limited, UK). Common Name Sectigo RSA Extended Validation Secure Server CA
So clearly the problem seems to lie with AVG.

Do you think you can have your IT developers fix this issue ?

Thanks for your help
Best regards
kevin

Dear Shawn. Thank you very much for your answer
unfortunatelly, https://cfspart.impots.gouv.fr still does not work for me.
Error code: SEC_ERROR_UNKNOWN_ISSUER
Issuer Name. Common Name: AVG untrusted CA
Configuration (see messages above):
MacBookPro. OSX. 10.11.6
AVG version is 19.8 (up to date, uninstalled and reinstalled)
(browsers tested on my computer: Firefox 78.10.0esr / Chrome 90.0.4430.85: these browser versions are said to be supported by the governmental Tax website. The problem is not with the website or browsers. I verified that website access works perfectly well on other computers with the same browsers (Firefox, Chrome, IE, Safari).
Thanks for your help
Best
kevin
Error code: SEC_ERROR_UNKNOWN_ISSUER
Issuer Name. Common Name: AVG untrusted CA


Thank you for the information, Kevin.
Please open AVG Internet Security/AVG antivirus free program.
Click on "Menu->About" and check whether it shows 21.3 version.
If not, refer this article (https://support.avg.com/SupportArticleView?urlname=Update-AVG-Antivirus) and perform the program update and restart your PC.
Please access the website and check whether you still get the certificate notice.
Keep us apprised about the status.

Hi Shawn.
Have you been able to address my comments above ?
Thanks a lot for your help
Bets regards
kevin
Thank you Balasubramanian,
I uninstalled and reinstalled AVG on my Mac. AVG vesrion is 19.8 and is said to be up to date.
I still can't access the governmantal website cfspart.impots.gouv.fr on my computer.
Error code: SEC_ERROR_UNKNOWN_ISSUER
Certificate issuer: AVG untrusted CA
Thank you for your help with the next steps
Best
Hi Kevin. Thank you for writing back and I apologize for the delayed response. I trust you had a nice weekend.

To resolve a disruption, it is necessary to replicate the disruption, which I have not been able to accomplish. It may be necessary to request a submitted system support file. 

However, I am still investigating this disruption, and I will let you know if it is necessary to request additional system information. In the interim, it is thankfully just one visited site you are experiencing disruption with, and not all visited sites. Thank you for your patience and understanding, and I will circle back to you soon. Regards, Shawn
Certificate cfspart.impots.gouv.fr
Subject Name
Serial Number130 004 955 00014
Inc. CountryFR
Business CategoryGovernment Entity
CountryFR
75012
LocalityParis
139 RUE DE BERCY
OrganizationDIRECTION GENERALE DES FINANCES PUBLIQUES
Common Namecfspart.impots.gouv.fr

Issuer Name
CountryCZ
State/ProvinceBrno
OrganizationAVG
Organizational UnitSoftware Development
Common NameAVG untrusted CA

Validity
Not Before2/9/2021, 1:00:00 AM (Central European Summer Time)
Not After3/13/2022, 12:59:59 AM (Central European Summer Time)

139 RUE DE BERCY
 

Hi Kevin. Thank you for your patience.

To further investigate the disruption you are experiencing, it will be necessary to request system logs.

I am going to send you an email, as associated to your AVG forum profile, that contains instruction to collect and submit system logs.

Thank you for your time and effort. Regards, Shawn

Dear Balasubramanian,
Thank you for your answer. The problem is not with the website or browsers. I verified that website access works perfectly well on other computers with the same browsers (Firefox, Chrome, IE, Safari). But on my computer, access is not authorized because supposedly the certificate issuer is an "AVG unstrusted CA". I simply don't understand why AVG does that ?
Thank you for your help if posssible

Hi Kevin,

We request you to reach the support of the website and inquire the reason behind this.
If not, you can post this on respective browser support page and ask them the reason.
You can also check whether the website is working on Internet Explorer.
Thank you.

Thank you for confirming, Kevin.
As you are using the latest version already, I'd request you to uninstall AVG, restart your PC and install AVG again as next troubleshooting step. 
Appreciate your patience and efforts so far.