Hi Delek,

Thanks for reaching out.

The error indicates that the Schema.org plugin is missing or not installed properly. Please try reinstalling the plugin, or disable it via the database if you can’t access the backend.

Let us know if you need help with that!

Best regards,

i cant access to administrator backend. how can i install the plugin?

https://issues.joomla.org/tracker/joomla-cms/44406

It seems to be a Joomla problem.

Q: What version of Joomla do you have there?

i have used your lates quickstart installer.

Ok.

Download Joomla 5.3.1 and from it take the /plugins folder, and upload on your site using FTP. Yes, override all files.

If that will not help, please share access to FTP

thanks. i will do it later. for now i have disabled the plugin Schemaorg and i can acess to front and backend. i will update you. thanks

Just want to share. seems it works.

1. disabled the plugin Schemaorg through database
2. access to to backend started working
3. updated the joomla 5.3.0 to 5.3.1 through backend.
4. automatically got reinstalled all the schemaorg plugins.