Install the plugin Kobo Metadata. It allows you to change the country you want the cover from (as long as Kobo supports said country). Not all covers downloaded will be high resolution. Most will be.
https://www.mobileread.com/forums/sh...d.php?t=355983
Also, go into the plugins preferences and see what plugins you have installed for downloading covers. Some work and some need help to work. Check if any are disabled.
For example, Kindle Hi-res Covers works with Kindle eBooks and for non-Kindle eBooks, you need to put the ASIN in the ID field.