I guess you have already read the Google Search Console documentation, but make sure that the URL is accessible and that it is not blocked by your robots.txt.
The URL doesn’t blocked by robots.txt
That URL works correctly, but https://3d-kstudio.com/sitemap-image-1.xml or https://3d-kstudio.com/sitemap-image-2.xml doesn’t and return error 404 instead of the sitemap.
Try to flush your permalinks.
Flushing permalinks didn’t help
xml from your other plugin works as expected