When a signature request expires it goes to state: EXPIRED and does not allow it to be signed. Through API you can extend its term through the method extendSignaturePeriod.
PUT {{endpoint}}/api/v3/set/extendSignaturePeriod
{
"setCode": "{{setCode}}",
"expires": 1652897955000
}
In the integration guide you have a chapter available with an explanation of use.
https://doc.viafirma.com/documents/api/latest/es/extendSignaturePeriod.html