When network activated, then network deactivated and later network activated again the rewrite rules are not flushed. In this situation displays could become inaccessible (404 Not Found) at their pretty permalinks for all sites other than the primary site. For example when other plugins flushed the rewrite rules between deactivation and activation.
When network activated, then network deactivated and later network activated again the rewrite rules are not flushed. In this situation displays could become inaccessible (404 Not Found) at their pretty permalinks for all sites other than the primary site. For example when other plugins flushed the rewrite rules between deactivation and activation.
Won't fix.
As suggested here..
https://jeremyfelt.com/2015/07/17/flushing-rewrite-rules-in-wordpress-multisite-for-fun-and-profit/
..this can be resolved by the owner of the network by visiting the WordPress admin Settings > Permalinks page, for each site in the network.