strange sitemap error

I'm encountering a strange error.

Some time ago I've changed the ip associated with my domain.
Immediately after that google wasn't able to locate the sitemaps and it
resulted in errors. After a day, I can see that sitemaps are being
downloaded in the sitemap control panel, but on the right of "last
downloaded" under "sitemap status" I can also see "not
found".

Any ideas what would be the remedy? I've tried resubmitting the
sitemaps and it didn't help. Should I delete the whole site and add
(verify) it again?