This ticket will be focused on replacing timecreated to timemodified when filtering recordings in the check_dismissed_recordings task. The way we handle dismissed recordings will have to be dealt with in https://tracker.moodle.org/browse/MDL-80225 

More information below:

If for some reason, a recording is not available when Moodle checks its availability, it will be marked as "RECORDING_DISMISSED".
The `mod_bigbluebuttonbn\task\check_dismissed_recordings` task has been modified in https://tracker.moodle.org/browse/MDL-76339 to verify dismissed recordings and re-enable them if they become available.
However, this task use a hardcoded limit of 30 days(RECORDING_TIME_LIMIT_DAYS) based on `bigbluebuttonbn_recordings.timecreated` field to filter which recordings should be check.
https://github.com/moodle/moodle/blob/e4d1369475eb0d7ebd69a21cd5ca277c6ed688cb/mod/bigbluebuttonbn/classes/recording.php#L791

So , for instance, if a recording was created 3 months ago (timecreated > 30 days) and is marked as dismissed, it will never become available again in Moodle. Even if the record is available on BBB server.

Since the `bigbluebuttonbn_recordings.timemodified` field is updated when a record is set to "RECORDING_DISMISSED", I think it would make more sense to use `bigbluebuttonbn_recordings.timemodified` to filter recordings to checks. This way only recordings not updated for more than 30 days would be ignored.
And ideally 30 days should be a default as stated in RECORDING_TIME_LIMIT_DAYS description https://github.com/moodle/moodle/blob/e4d1369475eb0d7ebd69a21cd5ca277c6ed688cb/mod/bigbluebuttonbn/classes/recording.php#L75 currently no setting allow us to override this value (but maybe this should be done in another dedicated issue).

Currently a workaround to re-enable those records is to regulary (through a dedicated cron task) run CLI script mod/bigbluebuttonbn/cli/update_dismissed_recordings.php which does not use time filtering.