Disable https with Putty (login to your DSM with http)

[Theet]

1) Log into your DS as root via SSH with putty
2) cd /etc
3) vi synoinfo.conf
4) press "/" and type "runHTTPS" without quotes of course, appropriate settings line will looks like this one: runHTTPS="yes".
5) press "i" key
6) change the runHTTPS="yes" to runHTTPS="no" on settings line
7) press ESC key
8) type ":wq" and press Enter (without quotes)
9) on command line type: /usr/syno/etc/rc.d/S97apache-sys.sh restart
10) open your web browser and try to connect to your DS on its IP address (ex. 192.168.1.15)

Now you should be able to connect to your DSM without HTTPS.