Hello.

Just turn on VPN server, add one user, and add firewall rule. Everything working fine.
But I have problem when more then one VPN session start via same username and password.
User establish VPN connection (no errors), but doesn't have access to local network, computers, printers.
I suspect, that this is due to the fact, that I input only one IP address in PPP->Secrets->User1->Remote Address and every new VPN session get same IP address.

Yes, you have to créate a pool for the VPN Profile like:

/ip pool
add name="VPN Pool" ranges=192.168.150.2/31

/ppp profile
set *FFFFFFFE local-address=192.168.150.1 remote-address="VPN Pool"

To get acces from VPN to local LAN:

/ip firewall filter
add chain=forward connection-state=established,related

Have the same troubles. I try to connect more than one pptp session to the MikroTik. The second VPN sessions stale on User login/password checking ant terminate with 806 error.
Try to investigate the reason. May be troubles are connected to the local firewall.