bot framework returning unauthorized after server reboot

Question

I have my bot. it's online. on a local machine the bot is working fine, but on the server it is returning unauthorized error. These are the iis logs

2016-12-30 23:06:44 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.78.21.180 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 93
2016-12-30 23:06:44 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.121.93.134 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 187
2016-12-30 23:06:45 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.127.183.46 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 374
2016-12-30 23:06:45 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.121.88.101 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 187
2016-12-30 23:06:45 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.127.183.46 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 374
2016-12-30 23:06:45 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.127.183.64 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 375
2016-12-30 23:06:47 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.121.93.134 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 187
2016-12-30 23:06:47 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.121.93.134 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 187
2016-12-30 23:06:47 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.127.183.64 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 374
2016-12-30 23:06:47 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.121.92.251 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 187
2016-12-30 23:06:48 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.127.183.46 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 390
2016-12-30 23:06:48 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.121.91.106 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 187
2016-12-30 23:06:48 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.121.93.134 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 187
2016-12-30 23:06:48 104.168.146.32 POST /rbots/mybot/api/messages - 443 - 40.78.17.157 BF-Facebook+(Microsoft-BotFramework/3.1++https://botframework.com/ua) - 401 0 0 78

we didn't do anything to the bot; however, suddenly it stopped working after the reboot. I gave full permission to the folder that's containing the bot, but still not working.