This has been suggested before. See https://forums.j-novel.club/topic/5349/what-are-the-chances-for-kokoro-connect-to-get-a-physcial-release for the relevant discussion.
While I enjoyed the anime it appears that there weren't enough ebook sales to justify a physical release. More people calling for it on the forum might help but I have no idea how well it sold as an e-book so it'd be difficult to speculate.
If you want an official take on it you would probably need to ask as part of a Q&A at a convention or announcement stream as JNC don't usually comment on specific commercial see decisions on the forums. You could also try getting the attention of Sam aka Quarkboy on Discord or Twitter or Reddit.