srcset shows original image url only

My website’s post thumbnails shows urls as original url only, as shown in the next example:

I have tried changing the theme to Twenty Nineteen, deactivating all plugins except for Woocommerce, regenerating thumbnails. But there isn’t any change. I also made sure that the different images sizes urls exist already, like https://example.com/wp-content/uploads/2020/07/example-150×150.jpg . It opens without any redirection, I have also an old staging website of the production website doesn’t have this issue and the urls are written correctly. It has some changes that I’m not sure of as I came late to the website. I have made a new clone of the website and it does have the issue. I suspect the hosting server, but don’t know how to check the source of the issue.

Please let me know if you needed any more info so that I edit the question to be more clear, thanks!