Question About PBN Indexing

Ok so I currently have a PBN network of about 20 sites and all of them are indexed in Google. However, I've noticed that a few of the sites ONLY have the homepage indexed in Google and none of the other posts/pages on the sites. All of the sites have original content and some have been active for months, there is no reason why these posts shouldn't be indexed by now.

This is concerning to me and am hoping someone can shed some light here. What could be the cause of this? Would this negatively be affecting the power of the site/anchor text link even though the link is still being picked up in crawlers from being on the homepage? Is it possible the site is penalized and I need to check it in Google WM ?

You need to build links to the internal pages and try to use mix of indexing services along with some services to get them indexed.