The two clips need to be pressed-in at the same time, then gently pull the two connectors apart.
The best is to use the specific tool shown in this photo, but you can get along also with a narrow tip pliers.
Normally the tool is sold in pairs, as it can also be used to screw/unscrew the cap that retain the cable.
If your connector has the two clips covered, it isn’t a Multicontact but a SUNCLIX connector, used in SMA inverters. The rick to open it is to stick one screw driver on one side only. The clip at the opposite side is automatically released. If you use two screw driver it is impossible to separate the two ends of the connector.