Can’t link posts imported to featured images

I’m having a problem linking posts to featured images. First, I uploaded images to the media library after importing a csv file to create posts. The name and path of the images are correct. I tried to set featured images by downloading images hosted elsewhere (http on local installation and https on remote site), using images currently in the Media Library and using images currently uploaded to wp-content / uploads \ wpallimport \ files \ (so I upload all images to the plugin directory). In all of these options, I checked the Set first image as highlighted image (_thumbnail_id) box. When I click on See and Test button, I can find the image on these three link images option. Tried with .csv, .xml and .sql. I saw the log and there was no error.