Hi,
Sometimes an extension is of a somewhat larger filesize. With slower hosting providers, uploading and installing might not succeed because of this. At client servers where I noticed this behaviour I used the seconds way of installing components etc. that Joomla offers.
Through ftp you should upload your UNZIPPED extension in a (simple named) folder and upload this in the folder 'tmp'.
SOmetimes extensions have weird folder names therefor I say 'simple folder name. So when you unzip the ChronoForms to your desktop, rename the unzipped folder to forms or something. Then up;oad that folder forms into the folder tmp.
Then go to Extensions > Install/Uninstall. On that page, you normally use the first line to browse and upload, but now go to the 2nd line. You should see it already filled in until the folder tmp, behind tmp add your folder name you uploaded, so it becomes.
blablabla/tmp/yourfolder/
Then click on install.