I have found what the problem with Arabic subtitle (maybe all other subtitle problem that is not working too) in here .
here is the summaries of the problem:
1- PMS can not convert context to utf8 (ERROR - Error opening conversion context from x-mac-cyrillic to utf-8)
2- some time subtitle content HTML codes (ex ) except () and any other thing like {\pos(195,110)} . I think PMS can not parse that.
I hope some one can fix that.