If you connect the WAN cable to your PC, do you need to set up Static IP to get internet as well? If yes, then it is normal that the MR200 needs static IP as well.
But if your PC can get IP automatically(Dynamic), then can clone the Ethernet MAC address of the PC to the MR200, then see if the MR200 can get the IP address.

Thanks for answer
If I use 3G/4G connection WAN port, the router get IP correctly from ISP on the WAN side; but if I use WAN Ethernet port connected to ISP (3G/4G for backup) this port no obtain IP fron DHCP server.

Roby