I had a random thought triggered by Indrajeet's answer that solved my problem.
When a new project is created in Xcode, a project folder is created. There is another folder in this folder with the same name as your project, a .xcodeproj file with your project name and yourProjectNameTests folder.
Visually like this.
Application_Name --> Application_Name Application_Name.xcodeproj Application_NameTests
When I had the error described above DropboxSDK.framework and its accompanying files were saved here in this folder: 
After deleting all the links to DropboxSDK.framework in my project, I decided to move DropboxSDK.framwork and accompanying files one level to the main folder Application_Name: 
As soon as I did this, I clicked File --> Add files to my project , went to the DropboxSDK.framework file, now one level of folders and added it to my project.
After assembly, there was no error. I restarted Xcode and tried again to make sure; still no error. Restart my computer to be sure ... there’s still no error!
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