Buen dia para todos.
Tengo un routerboard 750, con un problema:
Las conexiones PPTP para windows, funcionan perfectamente; En MacOs tengo dos equipos conectados sin problema bajo una IP Fija y conexion L2TP, pero cuando intento crear una nueva conexion en otro Mac, ya no me permite conectar, ni siquiera desconectando los anteriories.
Tengo ping a la direccion IP fija, desde cualquier equipo (con windows o mac) pero la vpn bajo mac ya no conecta. ayuda por favor.
Mil gracias a todos
Bienvenido al Foro, normalmente se utiliza el idioma ingles
Welcome to the Forum, English is normally used
Good day to everyone. I have a routerboard 750, with a problem: The PPTP connections for Windows work perfectly; I have two Macs connected without issue under a fixed IP and L2TP connection, but when I try to create a new connection on another Mac, it no longer allows me to connect, not even by disconnecting the previous ones. I can ping the fixed IP address from any device (whether Windows or Mac), but the VPN on Mac no longer connects. Help please. A thousand thanks to everyone.
If the Macs are setup the same and two work while one does not, I would probably start turning on some logging on the routerboard to see what the router reports. There should be a clue there. If not, then you would need to look on the logs on the Mac side and investigate further for answers.
I don’t usually have much trouble with Macs and VPN connection to Mikrotik, so if it were me, I would probably double and triple check configuration to be sure I hadn’t made a silly typo somewhere or something because I have been known to do that at times. 
All the OS makers are trying to get rid of l2tp and even more so pptp.
If you could possibly use wireguard, you would be a lot better off.
Need a preferably recent V7 routeros on your RB750 if it is a hex it should be fine,
if something older/less capable, you might get it working, but probably worth getting something newer.
Debugging such things usually starts with logging. What do you see in your router logs?
Moreover:
PPTP is long time outdated and deprecated.
So is L2TP.
The best solution is IKEv2 as both Mac and Windows have built-in clients.