4 gang wall socket question.

[Fastpedaller]

Well spotted - Yes, the 2 screw covers identify it as a 2 to 4 conversion. There are some well designed 'bits' available for electrical work: as an example, I fitted the kitchen in Daughters house last year and wanted to do a thorough, neat job with appliances plugged into sockets within adjacent base units with the supply from a switched fused outlet above the worktop for easy isolation if required. Two appliances (fridge and dishwasher), but no double independently switched fused outlet available. Putting 2 separate back boxes side -by-side looked messy and a gap between them wouldn't look good, and then I found a "1 +1" back box that gave a perfect solution!
https://www.screwfix.com/p/tower-db166lsf-1-1-gang-galvanised-steel-knockout-back-box-35mm/500aw

 

[Alex321]

The group clearly has one fuse, so if that had blown it would be all four sockets.

It could just be s loose connection inside, though I would except there again a single connection to the ring.

And the surge protection lamp is not lit.
Unless there is an obvious loose connection, I would be inclined to just replace the whole thing, since replacements aren't expensive.