Check the Friday's Tip of the Week if you're using UWP instead of MME MIDI. There is a known Windows bug that causes what you're describing. The tip also includes the registry fix to get you out of the hung condition.
 
Fnially, Windows 10 did a major update recently. Sometimes this means re-installing drivers. There are drivers for the 2x2m from December 2016, quite recent...try uninstalling the drivers then re-installing fresh. SONAR is hanging on something. 
 

I am using UWP because I am also running bluetooth for the Jamstik+ which has been working flawlessly. 

I found an older thread with a similar issue.  After trying everything, it was discovered to be caused by having his audio interface unplugged.
 
http://forum.cakewalk.com/Solved-SONAR-Platinum-will-not-start-m3179162.aspx
 

My interface was plugged in and I tried plugging it out and back in again, which didn't have any affect on it.  Restarted my computer a few times as well.  Ran Sonar as administrator and nothing was happening right still until I reinstalled/repaired the driver for the audio interface, but I have a strong feeling it has to do with what Anderton mentioned about with having UWP chosen for MIDI and I'm running Windows 10.  

In any case Sonar should "fail" safe without any drivers if it cannot connect.

Not sure if this will help but I have run into that issue on my W10 laptop. What happens is sonar hangs up when starting if I  have my outboard MK3 motu interface plugged into my usb. I then need to unplug the usb, restart sonar, then plug in the usb.
It can be a real pain. My W7 laptop has no problem with the usb being plugged in before I start sonar.
I perform with sonar on my w7 laptop a lot and have more than usual problems with the midi drivers in sonar with the last two sonar updates. I hope this is not the new trend for sonar updates. 

nathanielleemaloney
I am using UWP because I am also running bluetooth for the Jamstik+ which has been working flawlessly. 

Please, read the current Friday's Tip of the Week. Here are the relevant sections but you should really read the whole thing.
 

• If you try to open SONAR with UWP set in Preferences, SONAR may hang if you have a BLE-MIDI device selected as a MIDI input or output and the device is not connected via Bluetooth (note that connected and paired are two different states in Windows 10). The easiest way to solve this hang is to turn on the device before starting SONAR, and then switch to MME mode before turning off this device. Another tip: The hang/crash only occurs when using a Bluetooth MIDI output port. If only a MIDI input is used it will not hang, but will report that the port is not available on loading SONAR.
• If SONAR gets hung to the point where you can’t go into Preferences and return to MME, open the registry and go to HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR\Platinum. Click on Platinum, and set CoreMIDI to 0.