You said it cannot ping the outside interface of the firewall but you didn't specify what the actual "return" message was(See below).  If it can ping everything internally,  then chances are there is a routing or nat issue.  Windows 10 firewall may block echo reply or something stupid like that.
If your not using IPv6, try disabling that on the device first(Stab in the dark).  Next, I would verify the ip address, subnet mask and gateway like 10 times. Try setting a static IP in the subnet far away from the one it is currently using(trying to avoid acl's and duplicates here).  Otherwise, break out wireshark and do some troubleshooting.  I believe the SoUTM will allow packet captures on the interfaces through the GUI, but I haven't used it in a while.  Just need to determine where the packets are getting dropped.

ICMP Error Message's

1.) TTL Expired in Transit  <---Congestion on the network or other similar slow ass issue
2.) Destination Host Unreachable  <----Not Going out
3.) Request Timed Out   <----Not Coming Back
4.) Unknown Host   <---No DNS resolution (N/A if ping by IP)