Lets say that you have the local network 192.168.10.0/24
your mikrotik router 192.168.10.1 and your internet connection is PPPOE with dynamic IP address
you have DDNS name as (xyz.dyndns.org) or any other name.
you have NVR (192.168.10.100) on TCP port 9000

in normal configuration you will have the following entry on the NAT:
1- chain=srcnat action=masquerade out-interface=pppoe-out log=no log-prefix=""
2- chain=dstnat action=dst-nat to-addresses=192.168.10.100 to-ports=9000 protocol=tcp in-interface=pppoe-out dst-port=9000 log=no log-prefix=""

with this configuration you can access your server from outside with the address ( xyz.dyndns.org:9000 )
but from inside you will need to use the address ( 192.168.10.100:9000 )
its too noisy to have two configuration on your devices for each service you have.

i find many Hairpin NAT configuration online but its all work with normal interface (dynamic or static address) or with PPPOE but with static address
but nothings working with PPPOE with dynamic address.

finally i find this code solving the problem:
1- chain=srcnat action=masquerade out-interface=pppoe-out log=no log-prefix=""
2- chain=srcnat action=masquerade src-address=192.168.10.0/24 dst-address=192.168.10.0/24 log=no log-prefix=""
3- chain=dstnat action=dst-nat to-addresses=192.168.10.100 to-ports=9000 protocol=tcp dst-address-type=local dst-port=9000 log=no log-prefix=""

@Hussam THANKS MAN! I also got stuck on this Hairpin NATiing issue with Dynamic IP!

This line solved the issue!
THANKS AGAIN! Now I am at peace!

Lets say that you have the local network 192.168.10.0/24
your mikrotik router 192.168.10.1 and your internet connection is PPPOE with dynamic IP address
you have DDNS name as (xyz.dyndns.org) or any other name.
you have NVR (192.168.10.100) on TCP port 9000

in normal configuration you will have the following entry on the NAT:
1- chain=srcnat action=masquerade out-interface=pppoe-out log=no log-prefix=""
2- chain=dstnat action=dst-nat to-addresses=192.168.10.100 to-ports=9000 protocol=tcp in-interface=pppoe-out dst-port=9000 log=no log-prefix=""

with this configuration you can access your server from outside with the address ( xyz.dyndns.org:9000 )
but from inside you will need to use the address ( 192.168.10.100:9000 )
its too noisy to have two configuration on your devices for each service you have.

i find many Hairpin NAT configuration online but its all work with normal interface (dynamic or static address) or with PPPOE but with static address
but nothings working with PPPOE with dynamic address.

finally i find this code solving the problem:
1- chain=srcnat action=masquerade out-interface=pppoe-out log=no log-prefix=""
2- chain=srcnat action=masquerade src-address=192.168.10.0/24 dst-address=192.168.10.0/24 log=no log-prefix=""
3- chain=dstnat action=dst-nat to-addresses=192.168.10.100 to-ports=9000 protocol=tcp dst-address-type=local dst-port=9000 log=no log-prefix=""

Thank you, this was my problem also. With PPPOE dynamic for WAN, and an internal server for OVPN.

finally i find this code solving the problem:
1- chain=srcnat action=masquerade out-interface=pppoe-out log=no log-prefix=""
2- chain=srcnat action=masquerade src-address=192.168.10.0/24 dst-address=192.168.10.0/24 log=no log-prefix=""
3- chain=dstnat action=dst-nat to-addresses=192.168.10.100 to-ports=9000 protocol=tcp dst-address-type=local dst-port=9000 log=no log-prefix=""

Concur with 1 and 2 but not with 3................
You are missing one bit..... it should be
chain=dstnat action=dst-nat dst port=9000 protocol=tcp dst-address=!192.168.10.1 dst-address-type=local to-addresses=192.168.10.100

note1: if the too port is the same as dst port (no port translation required before hitting the firewall, the too port is not needed as an entry, as its implied).
note2: We include the part missing on purpose TO EXCLUDE the subnet from being the destination (as we are directing the request to a local interface and in this case to the pppoe interface).

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Another way of doing hairpin nat courtesy of steveocee is as follows:
/ip firewall nat
add action=masquerade chain=srcnat comment="HairpinNAT" src-address=192.168.10.0/24 dst-address=192.168.10.0/24 (new rule)
add action=masquerade chain=srcnat comment="NAT" out-interface=pppoe (standard rule)
add action=dst-nat chain=dstnat comment="Server" dst-port=9000 protocol=tcp dst-address-list=MYWANIP to-addresses=192.168.10.100 (modified standard rule)

Where MYWANIP is a firewall address list entry from IP Cloud.
(1) a. enable ip cloud
b. put in current WANIP and
c. capture the DNS name given
(2) a. create a firewall address list called MYWANIP and use the name from c. above for the address entry.