Updated Ubuntu Server - NC running into `502 Bad Gateway` when trying to access Collabora. No Docker

Hey, i had a running Nextcloud 24 up with Ubuntu 18.04 LTS and now i had to update Ubuntu - but now Collabora is not able to connect anymore. No changes to NC or Collabora.
According to the logs i’m running into a 502 Bad Gateway.
“Nextcloud Office” is showing me that it cannot access Collabora Online-Server.
Es konnte keine Verbindung zum Collabora Online-Server hergestellt werden.

The following is the received error when trying to access collabora.

[richdocuments] Fehler: GuzzleHttp\Exception\ServerException: Server error: `GET https://office.server.example/hosting/discovery` resulted in a `502 Bad Gateway` response:
<html>
<head><title>502 Bad Gateway</title></head>
<body>
<center><h1>502 Bad Gateway</h1></center>
<hr><center>ngin (truncated...)
 at <<closure>>

 0. /var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Middleware.php line 69
    GuzzleHttp\Exception\RequestException::create()
 1. /var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php line 204
    GuzzleHttp\Middleware::GuzzleHttp\{closure}("*** sensitive parameters replaced ***")
 2. /var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php line 153
    GuzzleHttp\Promise\Promise::callHandler()
 3. /var/www/nextcloud/3rdparty/guzzlehttp/promises/src/TaskQueue.php line 48
    GuzzleHttp\Promise\Promise::GuzzleHttp\Promise\{closure}("*** sensitive parameters replaced ***")
 4. /var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php line 248
    GuzzleHttp\Promise\TaskQueue->run()
 5. /var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php line 224
    GuzzleHttp\Promise\Promise->invokeWaitFn()
 6. /var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php line 269
    GuzzleHttp\Promise\Promise->waitIfPending()
 7. /var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php line 226
    GuzzleHttp\Promise\Promise->invokeWaitList()
 8. /var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php line 62
    GuzzleHttp\Promise\Promise->waitIfPending()
 9. /var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Client.php line 187
    GuzzleHttp\Promise\Promise->wait()
10. /var/www/nextcloud/lib/private/Http/Client/Client.php line 218
    GuzzleHttp\Client->request()
11. /var/www/nextcloud/apps/richdocuments/lib/WOPI/DiscoveryManager.php line 84
    OC\Http\Client\Client->get()
12. /var/www/nextcloud/apps/richdocuments/lib/WOPI/DiscoveryManager.php line 56
    OCA\Richdocuments\WOPI\DiscoveryManager->fetchFromRemote()
13. /var/www/nextcloud/apps/richdocuments/lib/WOPI/Parser.php line 41
    OCA\Richdocuments\WOPI\DiscoveryManager->get()
14. /var/www/nextcloud/apps/richdocuments/lib/TokenManager.php line 206
    OCA\Richdocuments\WOPI\Parser->getUrlSrc()
15. /var/www/nextcloud/apps/richdocuments/lib/Controller/DocumentController.php line 207
    OCA\Richdocuments\TokenManager->getToken("*** sensitive parameters replaced ***")
16. /var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php line 225
    OCA\Richdocuments\Controller\DocumentController->index()
17. /var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php line 133
    OC\AppFramework\Http\Dispatcher->executeController()
18. /var/www/nextcloud/lib/private/AppFramework/App.php line 172
    OC\AppFramework\Http\Dispatcher->dispatch()
19. /var/www/nextcloud/lib/private/Route/Router.php line 298
    OC\AppFramework\App::main()
20. /var/www/nextcloud/lib/base.php line 1023
    OC\Route\Router->match()
21. /var/www/nextcloud/index.php line 36
    OC::handleRequest()

GET /apps/richdocuments/index?fileId=526077&requesttoken=8rKbIBEaGhRkuQFFl%2F75eGuDmncrX9vV%2BiL7gFNztV4%3D%3AiNDxEEZsd3JW32sf%2FpnSLzHM7jVeMbCxrlepwQc%2B%2Bj0%3D&path=%2Ffolder-structure.doc
from 77.116.205.164 by xxx at 2022-06-25T13:53:12+02:00

I got that i used an old version of collabora and purged collabora now and installed it fresh, now the collabora service won’t start. Talked with someone and it seems now its the certs.