Hi @Phoenix1993, I see something with certificates.
Jun 25 08:00:31 Test-SSTP-FW accel-sstp[2132]: sstp: ssl-pemfile error: error:0909006C:PEM routines:get_name:no start line
Can you try to regenerate certificates like in this post SSTP server connection failed - #9 by Dmitry
Note: This modification only for linux SSTP client.