Nextcloud Office won't work

Nextcloud: 25.0.4
Apache: 2.4.54
PostgreSQL: 13.9
PHP: 8.8.28

I have installed Nextcloud Office app and as well Collabora Online Built-in CODE Server app. When I try to open an existing XLSX file or an existing DOCX file or when I create a new ODT file Nextxloud does not open an Office environment. Nothing, but a spinning wheel, happens until a notice is appearing:

Loading of the document name.odt has failed. Please try again later.

I have tried it later as well with the built-in CODE server as well as with the demo server of Collabora Productivity Ltd. Ireland. I have also left blank the field “Allow list for WOPI requests” and as well entered there 127.0.0.1 or 127.0.0.0. But in no case an Office environment appears.

In the live logs of my server I have found the following lines, eventually regarding the issue:

[Wed Mar 15 09:39:03 2023] [core:crit] [pid 71619:tid 140280937076480] (13)Permission denied: [client 195.50.157.123:50770] AH00529: /usr/www/users/glombim/data/.htaccess pcfg_openfile: unable to check htaccess file, ensure it is readable and that '/usr/www/users/glombim/data/' is executable
[Wed Mar 15 09:39:20 2023] [core:info] [pid 71083:tid 140279327745792] [client 78.46.0.106:52586] AH10247: Ignored invalid header value: Last-Modified: 'Wed, 15 Mar 2023 08:39:20'
[Wed Mar 15 09:39:20 2023] [core:info] [pid 72198:tid 140280476989184] [client 78.46.0.106:52602] AH10247: Ignored invalid header value: Last-Modified: 'Wed, 15 Mar 2023 08:39:20'
[Wed Mar 15 09:39:33 2023] [core:info] [pid 71619:tid 140279319353088] [client 78.46.0.106:53122] AH10247: Ignored invalid header value: Last-Modified: 'Wed, 15 Mar 2023 08:39:33'
[Wed Mar 15 09:39:34 2023] [core:info] [pid 71619:tid 140280920291072] [client 195.50.157.123:50770] AH10247: Ignored invalid header value: Last-Modified: 'Wed, 15 Mar 2023 08:39:34'
[Wed Mar 15 09:39:34 2023] [core:info] [pid 71619:tid 140280920291072] [client 195.50.157.123:50770] AH10247: Ignored invalid header value: Last-Modified: 'Wed, 15 Mar 2023 08:39:34'

What am I doing wrong?