What is/are the exact error message(s) ?

it is in the picture attached to the 1st message "technical error" in english that is all I get.

Where does the process break down? For example, when I click the link in your original question, it redirects to this page:

https://www.caisse-epargne.fr/particuliers

Does that page load for you?

When I click the red Accès aux comptes button, an overlay appears asking for Identifiant Client and showing a red Valider button.

Do you get the overlay? What happens when you submit that form?

I can't test this because I don't have an account.

If a site is generally known to work in Firefox, these are standard suggestions to try when it stops working normally:

Double-check content blockers: Firefox's Content Blocking/Tracking Protection feature, and extensions that counter ads and tracking, may break websites that embed third party content (meaning, from a secondary server).

(A) Do you see a shield icon toward the left end of the address bar, near the lock icon? More info on managing the Tracking Protection feature in this article: Enhanced Tracking Protection in Firefox for desktop (before Firefox 70: Content Blocking).

(B) Extensions such as Adblock Plus, Blur, Disconnect, DuckDuckGo Privacy Essentials, Ghostery, NoScript, Privacy Badger, uBlock Origin or uMatrix should provide toolbar buttons to manage blocked content in a page. There may or may not be a number on the icon indicating the number of blocked items; you may need to click the button to see what's going on and test whether you need to make an exception for this site.

Cache and Cookies: When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Clear Firefox's Cache

See: How to clear the Firefox cache

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, click the lock icon at the left end of the address bar. After a moment, a "Clear Cookies and Site Data" button should appear at the bottom. Go ahead and click that.

In the dialog that opens, you will see one or more matches to the current address so you can remove the site's cookies individually without affecting other sites.

Then try reloading the page. Does that help?

Testing in Firefox's Safe Mode: In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.)

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" Help > Restart with Add-ons Disabled
• (menu bar) Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

Indeed I get the main page then when I click on "accés au compte" I get the next overlay but once I enter my account login I get the error message before I can enter my access code.

On their website they explain how to clean up the cache for firefox and other methode to avoid errors so I tried that first but nothing worked.

And it's not only me, a client just called me to ask why he has same problem too. So I suspect all my clients in that bank will probably call me soon or later for that same reason.

I am computer tech btw.

I'll try the safe mode, haven't tried that yet.

Damn, it worked I never though about the safe mode before

I justed succefully log into my bank account in safe mode.

Apparently it's the new overlay windows from this bank that is now flaged as popup to block by Ublock Origin. I've been using Ublock for about as long as Firefox (+10years) and same bank since the 90s. I never though it could be that.

Thanks for helping me troubleshooting this guys.

Best Regards. M.N.

That was very good work. Well Done.
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