permalinks
post-migration
rewrite-rules
404s – Permalinks Not Flushed After Migration/Restore
404s appeared right after a site migration, restore, or server move; permalink structure hasn't been re-saved.
Read the fix htaccess rewrite-rules404s – Missing Rewrite Rules in .htaccess
.htaccess is missing the WordPress rewrite block entirely, or it was overwritten by another process.
Read the fix