It was really minor - mainly that I added the Dropbox REST API and then switched to the 52773 port...

Could have just put the revised links in, but was writing the update for a partner... copied your steps, ran through the process on IRIS 2020.1, so posted the updates here.

Minor Update for:

Managed File Transfer - setup for DropBox

Dropbox setup:

1. Create your DropBox account https://www.dropbox.com/
2. Create Your Dropbox App https://www.dropbox.com/developers/apps
   1. Click Create App
      1. Status - Development
      2. Permission Type: Full Dropbox
      3. Redirect URIs:  http://localhost:52773/csp/sys/oauth2/OAuth2.Response.cl
   2. Take note of the App Key and App Secret
3. Create new SSL Configuration - give it a name (eg  MFTTLSConfig )
4. Create new MFT Configuration: http://localhost:52773/csp/sys/sec/%25CSP.UI.Portal.MFT.Connection.zen?isNew=1
   1. Connection Name: Dropbox
   2. File Management Service: Dropbox
   3. SSL/TLS - pick the one from step above ( MFTTLSConfig )
   4. Email Address: for the Dropbox account
   5. Base URL: https://api.dropboxapi.com/2/
   6. OAuth 2.0 application name: The Name of the Dropbox App you created
   7. OAuth 2.0 client ID: <App Key> from Dropbox App
   8. OAuth 2.0 client secret: <App Secret> from Dropbox App
   9. OAuth 2.0 redirect URL: If you used the URI link above, then this should match
      1. Use TLS/SSL: UNCHECK
      2. Host Name: localhost
      3. Port: 52773
5. From the List http://localhost:52773/csp/sys/sec/%25CSP.UI.Portal.MFT.ConnectionList.zen you should now see the new Dropbox Connection Name
   1. Click - Get Access Token
   2. Status should now be "Authorized"

Interoperability setup:

Create new Business Operations:

1. For Documents FROM Dropbox
   1. Operation Class:  EnsLib.File.PassthroughOperation
   2. Operation Name: BO.StoreLocalFile
   3. File Path: <put the local path>
   4. File Name: leave the default - as it ensures it is unique %f_%Q%!+(_a)
2. For Documents TO Dropbox:
   1. Operation Class: EnsLib.MFT.Operation.Passthrough
   2. Operation Name: BO.StoreOnDropbox
   3. MFT Connection Name: <Connection Name from Above>
   4. Default MFT Folder: /yourfolderhere (note: it will create this folder if it does not exist)

Create new Business Services:

1. For Documents FROM Dropbox:
   1. Service Class: EnsLib.MFT.Service.Passthrough
   2. Service Name: BS.GetDropboxFiles
   3. MFT Connection Name: <Connection Name from Above>
   4. MFT SOURCE FOLDERS: /yourfolderhere (note: this folder has to exist or it errors)
   5. Target Config Names: BO.StoreLocalFile
2. For Documents TO Dropbox
   1. Service Class: EnsLib.File.PassthroughService
   2. Service Name: BS.SendFilesToDropBox
   3. File Path: <put local path here>
   4. File Spec: *
   5. Target Config Names: BO.StoreOnDropbox