Outdated self-signed cerificate keeps coming back

Installation: RPI4, ubuntu 20.94, latest NGINX, MariaDB, NC 19.0.3. letsencrypt & SCME. All works fine, just: users (on the same LAN) with Thunderbird/Windows, IOS and Android keep betting warnings about an invalid self-signed certificate, which expired in 2017. SSL Checker reports valid cert from Ler’s encrypt, only.

I can’t find the source of the ss-certificate and stop it.

Please provide a hint.

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Nextcloud version (eg, 18.0.2):
Operating system and version (eg, Ubuntu 20.04):
Apache or nginx version (eg, Apache 2.4.25):
PHP version (eg, 7.1):

The issue you are facing:

Is this the first time you’ve seen this error? (Y/N):

Steps to replicate it:

The output of your Nextcloud log in Admin > Logging:

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The output of your Apache/nginx/system log in /var/log/____:

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How do you access nextcloud on your local network? The same URL like outside?

The problem is probably your webserver configuration, that with local access, you use a different vhost configuration which has still the old self-signed certificate and not the letsencrypt one.

Hi tflidd, thx for advise. Yes, I am using the same URL and it works fine with the new cert from let’s encrypt. Thing I noted meanwhile: the old ss-cert did show on Thunderbird and Iphone and not on Honor6x. The H6s has been run empty and fully restarted meanwhile. Therefore I have erased the cache of TB and Iphone. Now I keep fingers crossed.