In addition to v29 being no longer supported, even within the v29 release cycle this installation is missing numerous maintenance releases (containing bug fixes).
Beyond updating this instance, the places to look (which are described in the support template) are:
- the Nextcloud server log
- your web browser inspectorConsole and Network tabs
Without the logs - as well as the server configuration - we’re all flying blind. It’s also generally not a good use for anyone’s time to troubleshoot a instance that isn’t kept up to date.
Your provider either needs to tackle this or you should perhaps find a better provider (or self host).