I have the same issue.
It looks like a bug on SmartThings latest app for Iphone I guess.
Here’s a thread about it:
https://community.smartthings.com/t/unable-to-install-custom-smartapps/92352/5
So I found a weird workaround.
If you tap New Fan Automation and wait until your iphone screen sleep ( be total black) than you unlock the fone again so the Smartthing App will come up. On my case the Automation was created without any name so I clicked and worked.
Give it a try 