> Can’t post anything on Damus on iOS 17.4. 

Have you used your private key with other nostr apps? Are you able to connect to relays on damus? 

> Can’t see zap icon on posts at all on Nostur or Damus

Yes, apple daggered damus so p2p zaps are more difficult than they should be. You can run https://nostrscript.suhailsaqan.com/ and restart damus to restore note zaps