Hi @andrewjohn95086
If the refrigerator is a Samsung RF24J9960S4/AA model variant here's the [document|30557|service manual] that may help.
Go to p.72 and when the refrigerator is not cooling as required, try the Section ''''2) ''Self-diagnostic function during normal operation'' procedure and check if there are any error codes being shown.
The error codes meaning and checks are shown on p.73→p.76.
Hopefully this is of some help.