hello
i´ve got the plesk versión 12.5.30 in my hosting but i don´t see the posibility of using let’s encrypt? is it normal? must i ask to my hosting to upgrade to another version of plesk or the problem is that the don´t allow the use of lets encrypt but i could use it in plesk 12.5.30?
best to talk to your provider about this 
plesk is a fairly specific plugin and it’s good to get advice from people who use it