AFAIK hive.blog wallet interface is still under construction, try Peakd.com for wallet management. It seems to work better when you log in using Hive Keychain.
Steem Keychain does not work on Hive. You will need Hive Keychain which is not yet published on browser extension stores but you can already get it from Github: How To: Install Hive Keychain from GitHub
Doesn't work on Peakd too, it says "Missing posting authority"... Any advice
I had the same issue when I used Hivesigner to log in to Peakd. I guess either Peakd or Hivesigner is using wrong key for the transaction.
I logged out, then I added my Hive/Steem password to Hive Keychain, logged in to Peakd using Hive Keychain and now it works