I am Pro, currently at 4.3.1
I successfully installed several extension except “Buddy” to go with iThemes BackupBuddy. In the installation dialog, the upper part says “Success”, while the actual install entry shows a red cross.
Are you trying to install extensions through the Dashboard > Extensions page, or by uploading a ZIP file?
Can you send us a screenshot of the issue so we have a better understanding of the context?