Problem with VPN connection

RouterOS Beginner Basics
1

Hello
I set up PPP VPN connection on router RB2011UiAS.
Unfortunately, sometimes users have problems to connect to VPN. I am begginer in Mokrotik so I completely don’t know what to check. Can you give me a small tip
?
I have guess that it’s problem after crash of computer or internet connection on user site. Probably they are disconnected after problem with Windows and they can’t connect again by some time.

2

Upolad some picture from your vpn to see where the wrong