FortiClient is not connecting

Hello,

I got a Forticlient and I cant connect to my business network. Then I tried the same with a different computer but its working there and I dont know why.

VPN that the client works:

Windows 10 x64

FortiClient: 5.4.3.0870

User:beck

working: yes

VPN that the Client doesnt work:

Windows 8.1 x64

FortiClient: 5.4.3.0870

User: beck

working: no

Error Message: the log is attached

Thank you