Sometimes, it can be due a host settings or other reasons. Thus, you have to follow alternative way.
Step 1
Download ST Kit to your local disk.
Step 2
Go to Plugins > Add New > Upload and select stkit.zip file from your local disk.
Step 3
Once ST Kit is installed you’ll be prompted to activate plugin. Do it.
Congratulations!
The theme has been installed completely. Go to the next steps.