I believe there is a exponential backoff mechanism in place if an instance cannot push to an other’s inbox, so other instances may not have any attempt left to retry if it has been two days. In my experience un-subscribing then re-subscribing to an instance’s community was enough for it to send posts after a few hours.
I use Readeck which has a few extra features over Pocket and bookmarks: offline copy, sharable link to said copy, highlights, bookmarks collection and the ability to export saved articles to ebook. Oh and it’s self-hostable.
Personnaly, I mostly use it to bookmark and highlight articles I have read, with some bookmarked to read later.