Conversions are not created

[benounnas]

i defined a media conversion in my model to add thumbnails of videos, it returned the path of the thumbnail but it didn't create it when i checked the folder.
My project manager i should check the queue worker which is not mentioned i think in the documentation (or i missed it may be), i run php artisan queue:work i had this error:
Declaration of Symfony\Component\Cache\CacheItem::expiresAt(?DateTimeInterface $expiration): static must be compatible with PsrExt\Cache\CacheItemInterface::expiresAt($expiration)
After googling a little bit, i found an answer (https://stackoverflow.com/a/67221583/9767267), i had to delete the psr extension from my system (Debian based), and it worked.
If it is a beginner issue, please can you add at least a small details when it comes to generating conversions in the "defining conversions' page.