So, after opening a thread here and spending hours, I finally managed to identify my issue.

Long story short, many pictures were not shown on the site after uploading it on namecheap hosting (it was created on the localhost).

I found that since our images had previously different characters (é for example), once uploaded to the store it became (?), thus, no images were shown.

After talking to namecheap support for more than 10 times, they concluded that they can't do anything.

Now, we have more than 5000 pictures on the site so no way to edit one by one as that will take days. I4m not even sure if there is a solution to this. please help