Oqallisissiat Howard Miller-imit allatat

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The plugin details show only versions up to Moodle 4.0. This might mean that it doesn't work on 4.1. You should probably contact the developer to ask what their intentions are. If they do not intend to support it then it's probably best avoided (seeing as we are now at 4.4).

You can install it manually (https://docs.moodle.org/404/en/Installing_plugins#Installing_manually_at_the_server) but you then need to carefully check it actually works.
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Well, set it to 365 days seems like a good start. Why would you set it to 1000 if you want 365?

By default the cleanup task runs daily. You can configure the task to run more frequently if you want. Have you checked the the task is working? Is cron working at all on your system?
 
I have no idea what you mean by "The scheduled tasks do not have the time to clean up"