Office LAN subnet Can not ping all devices in DMZ

Our office LAN subnet is 10.141.101.x and we have a DMZ subnet 192.168.81.x , in this dmz we have a TMG server with ip, also a NAT router and SSL vPN devices, and we use a proxy server here and all our pc is pointing to this TMG server in DMZ, suddenly today all our office LAN subnet 10.141.101.x can not ping the TMG server, we only be able to ping the NAT router in DMZ, and I have tired to put a notebook in the DMZ, and use ip scan tool to scan the DMZ subnet, I could found all the ip in DMZ, only from the office subnet can only scan for two ip in DMZ, ssl VPN device and NAT router, we haven't changed anything , just suddenly don't work any idea what went wrong ?
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Try deleting  all the ping rules and rebuilt the original rule (From: Internal, LocalHost, VPN, Perimiter - To: Internal, LocalHost, VPN, Perimiter, External).

Then re-start your server.

Also to understand what is going wring start a TMG Log Query.

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