I still cant work out what happens when you press the install button - presumably nothing?
One more thing you might try. It is possible the ota app cannot get a data connection, especially if you are using wifi.
Try this.
Click in the top right corner of the OTA app, if you see an option related to WiFi only for downloads, untick it.
If this works and you're asked whether to wipe cache or data as well, select data.
Try it now.
If you are not connected to your router by an ethernet cable i would also recommend that.