Hi,
At the end i could resolve it, you just need to change the last line to the size you need (i put 1000, that i think it is going to be enough).
Then, and this is so important, is to install the Regenerate Thumbnails plugin, and regenerate all the images, because if not, you are not going to see any change.
After doing this, everything works perfectly.
I hope this helps anyone else.
🙂
PD: I need the full size featured image in the preview of the post, inside the post the image is already full size. I hope you can help me.
Thank you so much
