One may encounter this very annoying error when migrating your WordPress Multisite installation or changing the domain name for it. For some reason seems that WordPress once in a while is missing to properly update domain values, so you may need to do it manually. So please take a look at these two locations to make sure that all the domain names match with you current setup. Variable $wpe_all_domains you will find in the wp-config.php file and it will look something like this:

$wpe_all_domains=array ( 0 => 'site1.domain.com', 1 => 'site2.domain.com', 2 => 'site3.domain.com', 3 => 'site4.domain.com', 4 => 'site5.domain.com', 5 => 'site6.domain.com', 6 => 'site7.domain.com', 7 => 'site8.domain.com', 8 => 'site9.domain.com', 9 => 'site10.domain.com', 10 => 'site11.domain.com', );

And then head to your database and find the tables wp_blogs and wp_domain_mapping which contain all the registered domains and do the same.

Enjoy your MultiSite!