Cannot change Logo - php.ini is set correctly

Dear all,

I am facing an issue in the sense that Nextcloud does not allow me to change the log-in logo due to limited file size (see attached picture

The file I would like to upload is 25.6 kb big. I checked my php.ini: upload_max_filesize = 20G and post_max_size = 20G (as I defined it during the installation)
I am logged in as ‘admin’. I am really somewhat clueless what to do. I hope I could get some input from you guys.